Test element for electrochemically detecting at least one analyte

ABSTRACT

A test element for electrochemically detecting at least one analyte in a bodily fluid is disclosed. The test element comprises at least one first electrode and at least one second electrode. The first electrode is designed as a working electrode and the second electrode is designed as a counter electrode. The test element comprises at least one capillary capable of receiving a sample of the body fluid. The first electrode and the second electrode are arranged on opposing sides of the capillary. The first electrode and the second electrode are arranged such that during a capillary filling the first electrode and the second electrode are wetted simultaneously and at an equal rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/EP2015/080132, filed 17 Dec. 2015, which claims the benefit ofEuropean Patent Application No. 14199341.0, filed 19 Dec. 2014, thedisclosures of which are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a test element for electrochemicallydetecting at least one analyte, a method for producing the test elementand a system for determining at least one property of a sample. Themethod and devices according to the present disclosure may be used fordetecting at least one analyte present in one or both of a body tissueor a body fluid, in particular the method and devices are applied in thefield of detecting one or more analytes such as glucose, lactate,triglycerides, cholesterol or other analytes, typically metabolites, inbody fluids such as blood, typically whole blood, plasma, serum, urine,saliva, interstitial fluid or other body fluids, both in the field ofprofessional diagnostics and in the field of home monitoring. However,other fields of application are feasible.

BACKGROUND

In the field of medical technology and diagnostics, a large number ofdevices and methods for detecting at least one analyte in a body fluidare known. The method and devices may be used for detecting at least oneanalyte present in one or both of a body tissue or a body fluid, inparticular one or more analytes such as glucose, lactate, triglycerides,cholesterol or other analytes, typically metabolites, in body fluidssuch as blood, typically whole blood, plasma, serum, urine, saliva,interstitial fluid or other body fluids. Further devices are known formeasuring activating times, e.g., a thrombin activation time measurementfor coagulation monitoring. Without restricting the scope of the presentdisclosure, in the following, mainly reference is made to thedetermination of glucose as an exemplary and typical analyte.

The determination of blood glucose concentration as well as acorresponding medication is an essential part of daily routine for manydiabetics. In order to increase convenience and in order to avoidrestricting the daily routine by more than a tolerable degree, portabledevices and test elements are known in the art, such as for measuringblood glucose concentration during work, leisure or other activitiesaway from home. In the meantime, many test devices are commerciallyavailable. A large number of test devices and test systems are knownthat are based on the use of test elements in the form of test strips.Applications are known, in which a multiplicity of test strips isprovided by a magazine, wherein a test strip from the magazineautomatically may be provided to the testing device. Other applications,however, are known in which single test strips are used, which areinserted into the testing device manually by a user. Therein, typically,the end of the test strip is adapted to be inserted into the testingdevice and for detecting the analyte, wherein the opposing end of thetest strip serves as a handle enabling the user to push the test stripinto the testing device or to remove the test strip from the testingdevice. For applying the sample to the test element, typical testelements provide at least one sample application site, such as acapillary opening in capillary test elements or a spreading layer, i.e.,net or mesh-like structure used to spread and/or distribute the sampleto what can be underlying layers in optical test strips having a topdosing system. Test strips of this type are commercially available,e.g., under the trade name ACCU-CHEK ACTIVE®. Alternatively to home careapplications, such test elements may be used in professionaldiagnostics, such as in hospital applications.

In many cases, for detecting the analyte, test elements are used, suchas test strips, which comprise one or more test fields having one ormore test chemistries. The test chemistries are adapted to change one ormore detectable properties in the presence of the analyte to bedetected. Thus, electrochemically detectable properties of the testchemistry and/or optically detectable properties of the test chemistrymay be changed due to the influence of the presence of the analyte. Forpotential test chemistries that may be used within the presentdisclosure, reference may be made to J. Hones et al.: DiabetesTechnology and Therapeutics, Vol. 10, Supplement 1, 2008, S-10 to S-26,the disclosure of which is hereby incorporated herein by reference.However, other types of test chemistries may be used within the presentdisclosure.

In general, the detection of the at least one analyte can be performedby using an electrochemical test element. Commonly used are disposableelectrochemical capillary sensor test elements. Such test elementstypically comprise at least one working electrode for detecting theanalyte as well as at least one counter electrode to support a currentflow through a measuring cell of the test element. In addition,optionally, the test element may comprise at least one referenceelectrode. In alternative embodiments, a reference electrode may bedesigned individually and/or may be combined with the counter electrode.However, other types of measurement setups are possible, in order toderive an analyte concentration from a comparison of electrodepotentials.

Such test elements typically comprise a measuring cell. The measuringcell may be a capillary configured to aspirate a liquid sample embeddedbetween at least two electrode surfaces, in particular of the workingelectrode and the counter electrode. A voltage between the at least twoelectrodes may be applied and a responding current is detected andconverted into a concentration value of the at least one analyte.Typically, the counter electrode is provided in order to close anelectric circuit to the working electrode. For this purpose, typically,redox currents and/or, to a lower extent, capacitive charging currentsare used. Typically, the working electrode comprises at least onedetector substance adapted to perform an oxidation reaction and/or areduction reaction with the analyte. In many cases, the detectorsubstance comprises at least one enzyme such as glucose oxidase (GOD).In case the detection reaction comprises an oxidation reaction at theworking electrode, the counter electrode typically provides a reductionreaction in order to close the electric circuit.

Specifically, the working electrode may be covered by at least onereagent layer. Often the reagent layer may comprise an enzyme with aredox active enzyme co-factor to support a specific oxidation of theanalyte in the body fluid. The reagent layer may comprise further aredox cycle providing substance, which may act as an electron acceptor.The redox cycle providing substance may react with the enzyme co-factorand may transport electrons taken from the enzyme cofactor to theelectrode surface by diffusion. At the electrode surface, a redoxmediator may be oxidized and the transferred electrons may be detectedas a current. The current may be proportional to a concentration of theanalyte in the body fluid. When applying the liquid sample to themeasuring cell, the reagent may get dissolved and a measuring processcan be started by applying the voltage. The voltage is commonly appliedto the electrodes by using conductive contact pads arranged at one endof the test strip connected with conductive traces along the test strip.

Generally the working electrode may be designed as in blood glucose testelements, such as test elements commercially available, e.g., under thetrade name ACCU-CHEK AVIVA® or the trade name ACCU-CHEK PERFORMA®, or asin coagulation monitoring test elements, such as test stripscommercially available, e.g., under the trade name COAGUCHEK®. Thus, aplastic foil may be used as a test carrier, which may be covered with atleast one conductive layer building at least one contact, conductivetraces and electrode supports. The conductive layer may be sputtered asa thin metal film directly on the test carrier and may be structured byone or more of laser etching, laser ablation or lithography.Alternatively, the structures may be created by screen or inkjetprinting processes. The reagent layer may be applied to the test carrierby one or more of coating, printing or dispensing.

The working electrode may be of one or more of a noble metal, such asgold, palladium, platinum, or carbon in form of graphite or glassycarbon. For example, gold is used in ACCU-CHEK

AVIVA®, ACCU-CHEK PERFORMA®, and COAGUCHEK® test strips. Firstly, goldis a very expensive material. Further, the counter electrode may even bemade from a reducible material. In the art, redox materials such asAg/AgCl systems are known, such as for combined counterelectrodes/reference electrodes. In this case, the available oxidationpotential of the gold working electrode versus an Ag/AgCl electrode islimited to about 700 mV and gold will get oxidized at higher voltages,which may cause high, unpredictable background currents.

Alternatively to gold, graphite electrodes may be used. Graphite may beused as a paste or ink, containing also organic components allowing acoating process. Thick graphite films may be structured by screenprinting or a similar process. However, the printed graphite electrodesurfaces may have relative high tolerances and may cause higherimprecisions compared to a sputtered, laser ablated gold electrode. Alltypes of test elements with electrodes produced in such electrodestructuring processes require an exact positioning in laminationprocesses, wherein the structured test carrier and the capillarystructure are assembled. Thus, a manufacturing process of such a teststrip may be complex, expensive and inflexible. Further, structures ofthe test elements, as dimensions of the test elements, are fixed andcannot be changed easily to produce variants of the test strip.

In test elements commonly used, the electrodes may be arranged in acoplanar configuration. Due to manufacturing costs and processcomplexity, is may be desirable to produce the electrodes during oneproduction process, such as during one lamination process. Samples ofthe body fluid may be taken by pricking a finger tip by a user, forexample in a self-testing or a home care application. These samples mayhave small volumes, such as volumes smaller than 2 μl. Hence, acapillary volume suitable for these samples has to be small, such thatfor production reasons it may be only possible to coat the at least twoco-planar electrodes with the same reagent stripe in one laminationprocess. Thus, active ingredients in the reagent must not only supportan analytical detection reaction at the working electrode, they alsohave to support electrode reactions on the counter electrode. However,this may set limits for usable chemistry options: the reagent has to bestable in liquid during a coating process, which may last up to sevendays; the reagent must not interfere with redox active substances in thesample; and the working electrode current must not cut off by a limitedcounter electrode reaction.

An opposing electrode configuration allows the working and the counterelectrode to be coated with separate reagents. For example, the counterelectrode may be coated with an Ag/AgCl paste. However, the knowndevices with opposing electrode configurations reveal disadvantages. Inparticular, coating and drying processes of a manufacturing process ofthe electrodes cannot be performed together, but have to be performed inparallel or separate process steps. Therefore, the manufacturing processmay be complex and thus expensive. Further, the attainable volume of thecapillary may be higher compared to strip designs with one reagentstripe.

Further, as outlined above, a required electrode shape and/or structureof known electrodes may be disadvantageous. In A. Heller and B. Feldman:Electrochemistry in Diabetes Management, Accounts of chemical research,Vol. 43, No. 7, July 2010, 963-973, a test strip with an opposingelectrode configuration is shown. However, the described test striprequires electrodes with a specific electrode structure. Therefore, anexact positioning is required and thus the manufacturing process may becomplex and expensive.

Known test elements for home care and/or self-testing applications mayhave a front dosing or side dosing position for dosing or application ofthe sample into the capillary. As outlined above, a sample of the bodyfluid may be taken by pricking a finger tip. Commonly, capillaryopenings may be arranged on a front edge or a side edge of the testelement. However, for the usage in professional settings, such as inhospitals, a significant part of the overall testing may be from venousor arterial blood taken from sample tubes, so that transfer devices likepipettes, glass capillaries or syringes have to be used for dosing orapplication of the sample. Thus, capillary openings on the front edge orthe side edge may be not convenient and difficult to handle with thosetransfer devices.

Thus, there is a need in the art for a test element, which can bemanufactured in an easy and cost effective process, such as without anypositioning dependent alignment required in the whole manufacturingprocess. Further, a sample dosing to the test elements shall beconvenient and easy to handle both in home care and in professionaldiagnostics applications.

SUMMARY

It is against the above background that the embodiments of the presentdisclosure provide certain unobvious advantages and advancements overthe prior art. In particular, the inventors have recognized a need forimprovements in a test element for electrochemically detecting at leastone analyte, a method for producing a test element and a system fordetermining at least one property of a sample.

In accordance with one embodiment of the present disclosure, a system isprovided for determining at least one property of a sample, the systemcomprising at least one test element, wherein the test element comprisesat least one first electrode and at least one second electrode, whereinthe first electrode is designed as a working electrode and the secondelectrode is designed as a counter electrode, wherein the test elementcomprises at least one capillary capable of receiving a sample of thebody fluid, wherein the first electrode and the second electrode arearranged on opposing sides of the capillary, wherein the first electrodeand the second electrode and the capillary in between the firstelectrode and the second electrode form an electrochemical cell, whereinthe test element is configured to detect the at least one analyteindependently of a filling level of the electrochemical cell, whereinthe first electrode and the second electrode are arranged such thatduring a capillary filling the first electrode and the second electrodeare wetted simultaneously and at an equal rate, the system furthercomprising at least one measurement device adapted for performing atleast one electrical measurement using the test element, wherein themeasurement device is configured to detect both an AC signal and a DCsignal, and wherein the measurement device is configured to detect theat least one analyte independently of a filling level of theelectrochemical cell.

In accordance with another embodiment of the present disclosure, amethod for determining at least one property of a sample is provided,wherein a system according to an embodiment of the disclosure is used,and wherein the method comprises the following steps: a) connecting thetest element to at least one measurement device; b) applying a sample ofbodily fluid to a capillary of at least one test element; c) determiningboth an AC signal and a DC signal with said measurement device; and d)calibrating measurement results by using the AC and DC signal.

In accordance with yet another embodiment of the present disclosure, atest element for electrochemically detecting at least one analyte in abodily fluid is provided, wherein the test element comprises at leastone first electrode and at least one second electrode, wherein the firstelectrode is designed as a working electrode and the second electrode isdesigned as a counter electrode, wherein the test element comprises atleast one capillary capable of receiving a sample of the body fluid,wherein the first electrode and the second electrode are arranged onopposing sides of the capillary, wherein the first electrode and thesecond electrode and the capillary in between the first electrode andthe second electrode form an electrochemical cell, wherein the testelement is configured to detect the at least one analyte independentlyof a filling level of the electrochemical cell, wherein the firstelectrode and the second electrode are arranged such that during acapillary filling the first electrode and the second electrode arewetted simultaneously and at an equal rate, wherein the capillary isopen at three sides, wherein a sample of bodily fluid is applicable toone or both of a side dose position or a front dose position, whereinthe test element comprises a first electrode contact zone and a secondelectrode contact zone configured to contact the first electrode and thesecond electrode with a further device, wherein the first electrodecontact zone and the second electrode contact zone are arranged indifferent layers of a layer setup of the test element, wherein one ofthe first electrode contact zone and the second electrode contact zoneprotrudes over the other one of the first electrode contact zone and thesecond electrode contact zone, wherein the first electrode contact zoneand the second electrode contact zone are configured to be electricallycontacted from opposing sides of the test element, wherein the testelement comprises a layer setup, wherein the first electrode comprisesat least one first electrode conductive layer disposed on at least onefirst electrode carrier layer, wherein the second electrode comprises atleast one second electrode conductive layer disposed on at least onesecond electrode carrier layer, and wherein at least one spacer layer isdisposed in between the first electrode conductive layer and the secondelectrode conductive layer.

In accordance with still another embodiment of the present disclosure, amethod for producing a test element according to an embodiment of thepresent disclosure is provided, the method comprising at least one stepof forming a layer setup, wherein the first electrode, the secondelectrode and the capillary are formed such that the first electrode andthe second electrode are arranged on opposing sides of the capillary,wherein the test element is produced in a continuous process and themethod further comprising cutting the layer setup into test strips.

These and other features and advantages of the embodiments of thepresent disclosure will be more fully understood from the followingdescription in combination with the drawings and accompanying claims. Itis noted that the scope of the claims is defined by the recitationstherein and not by the specific discussion of features and advantagesset forth in the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the presentdisclosure can be best understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 shows a layer setup of an embodiment of a test element accordingto the present disclosure;

FIG. 2 shows an exploded drawing of the test element according to thepresent disclosure;

FIG. 3A shows a system according to the present disclosure and aperspective, cross-sectional view of the test element;

FIG. 3B shows another view of a system according to the presentdisclosure and a cross-section of the test element;

FIG. 4A shows a histogram of an impedance measurement of a failsafemeasurement;

FIG. 4B shows a histogram used for monitoring a filling process;

FIG. 5A shows a second embodiment of a test element according to thepresent disclosure;

FIG. 5B shows a cross-section of the second embodiment of the testelement;

FIG. 6 shows an exploded drawing of the second embodiment of the testelement;

FIG. 7 shows layers of the test element according to the secondembodiment in different manufacturing steps;

FIG. 8A shows a third embodiment of a test element according to thepresent disclosure;

FIG. 8B shows the third embodiment of the test element;

FIG. 8C shows a cross-section of the third embodiment of the testelement;

FIG. 9 shows an exploded drawing of the third embodiment of the testelement;

FIG. 10 shows layers of the test element according to the thirdembodiment in different manufacturing steps;

FIG. 11 shows an exploded drawing of an embodiment of the test elementaccording to the present disclosure;

FIG. 12 shows an exploded drawing of an embodiment of the test elementaccording to the present disclosure;

FIG. 13A shows a top view and a bottom view of the embodiment of thetest element of FIG. 12; and

FIG. 13B shows a top view and a bottom view of the embodiment of thetest element of FIG. 12.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help improve understandingof the embodiment(s) of the present disclosure.

DETAILED DESCRIPTION

As used in the following, the terms “have”, “comprise” or “include” orany arbitrary grammatical variations thereof are used in a non-exclusiveway. Thus, these terms may both refer to a situation in which, besidesthe feature introduced by these terms, no further features are presentin the entity described in this context and to a situation in which oneor more further features are present. As an example, the expressions “Ahas B”, “A comprises B” and “A includes B” may both refer to a situationin which, besides B, no other element is present in A (i.e., a situationin which A solely and exclusively consists of B) and to a situation inwhich, besides B, one or more further elements are present in entity A,such as element C, elements C and D or even further elements.

Further, as used in the following, the terms “preferably”, “morepreferably”, “particularly”, “more particularly”, “specifically”, “morespecifically” or similar terms are used in conjunction with optionalfeatures, without restricting alternative possibilities. Thus, featuresintroduced by these terms are optional features and are not intended torestrict the scope of the claims in any way. The invention may, as theskilled person will recognize, be performed by using alternativefeatures. Similarly, features introduced by “in an embodiment of thedisclosure” or similar expressions are intended to be optional features,without any restriction regarding alternative embodiments of thedisclosure, without any restrictions regarding the scope of thedisclosure and without any restriction regarding the possibility ofcombining the features introduced in such way with other optional ornon-optional features of the disclosure.

In accordance with an embodiment of the present disclosure, a testelement for electrochemically detecting at least one analyte of a bodilyfluid is disclosed. As further used herein, the term “analyte” may referto an arbitrary element, component or compound, which may be present ina body fluid and the concentration of which may be of interest for auser or a patient. Typically, the analyte may be or may comprise anarbitrary chemical substance or chemical compound that may take part inthe metabolism of the patient, such as at least one metabolite. As anexample, the at least one analyte may be selected from the groupconsisting of glucose, cholesterol, triglycerides, lactate. Additionallyor alternatively, however, other types of analytes may be used and/orany combination of analytes may be determined. Generally, an arbitrarytype of body fluid may be used. As generally used within the presentdisclosure, the term “patient” may refer to a human being or an animal,independent from the fact that the human being or animal, respectively,may be in a healthy condition or may suffer from one or more diseases.As an example, the patient may be a human being or an animal sufferingfrom diabetes. However, additionally or alternatively, the invention maybe applied to other types of users or patients.

The body fluid may be a body fluid that is present in a body tissue ofthe patient, such as in the interstitial tissue. Thus, as an example,the body fluid may be selected from the group consisting of blood andinterstitial fluid. However, additionally or alternatively, one or moreother types of body fluids may be used. The body fluid generally may becontained in a body tissue.

As used herein, the term “test element” refers to an arbitrary devicethat is capable of detecting the analyte in the body fluid, typically bycomprising at least one component that changes at least one detectableproperty when the analyte is present in the body fluid, such as a testchemistry, for example one or more known test chemistries disclosed inthe prior art. The term “test chemistry” refers to an arbitrary materialor a composition of materials adapted to change at least one detectableproperty in the presence of the at least one analyte. Generally, thisproperty may be selected from an electrochemically detectable propertyand/or an optically detectable property, such as a color change and/or achange in remissive properties. Specifically, the at least one testchemistry may be a highly selective test chemistry, which only changesthe property if the analyte is present in a sample of a body fluidapplied to the test element, whereas no change occurs if the analyte isnot present. More typically, the degree or change of the at least oneproperty is dependent on the concentration of the analyte in the bodyfluid, in order to allow for a quantitative detection of the analyte. Asan example, the test chemistry may comprise at least one enzyme, such asglucose oxidase and/or glucose dehydrogenase. Additionally oralternatively, the test chemistry may comprise one or more co-enzymesand/or one or more mediators. Further, alternatively or additionally,the test chemistry may comprise one or more dyes, which, typically ininteraction with the one or more enzymes, may change their color in thepresence of the at least one analyte to be detected.

As used herein, the term “electrochemically detection” refers to adetection of an electrochemically detectable property of the analyte,such as an electrochemical detection reaction. Thus, for example, theelectrochemical detection reaction may be detected by comparing one ormore electrode potentials, such as an electrostatic potential of aworking electrode with the electrostatic potential of one or morefurther electrodes such as a counter electrode or a reference electrode.The detection may be analyte specific. The detection may be aqualitative and/or a quantitative detection. The test element may be astrip-shaped test element.

As used herein, the term “strip-shaped” refers to an element having anelongated shape and a thickness, wherein an extension of the element ina lateral dimension exceeds the thickness of the element, such as by atleast a factor of 2, typically by at least a factor of 5, more typicallyby at least a factor of 10, and most typically by at least a factor of20 or even at least a factor of 30. The test element may be a teststrip.

The test element comprises at least one first electrode and at least onesecond electrode. The first electrode is designed as a working electrodeand the second electrode is designed as a counter electrode. As usedherein, the term “electrode” refers to an entity of the test elementthat is adapted to get in contact with the body fluid, either directlyor via at least one semipermeable membrane or layer. Each electrode maybe embodied such that an electrochemical reaction may take place at theelectrode. Thus, the electrodes may be embodied such that an oxidationreaction and/or a reduction reaction may take place at the electrodes.As used herein, the term “working electrode” refers to an electrodebeing adapted for performing at least one electrochemical detectionreaction for detecting the at least one analyte in a body fluid. Thus,the working electrode may comprise at least one reagent, such as onetest chemistry. As used herein, the term “counter electrode” refers toan electrode adapted for performing at least one electrochemical counterreaction adapted for balancing a current flow required by the detectionreaction at the working electrode. The test element may further compriseat least one reference electrode, for example a combined counterelectrode/reference electrode system. As used herein, the term workingelectrode refers to an electrode being adapted for performing at leastone electrochemical detection reaction for detecting the at least oneanalyte in a body fluid.

The first electrode and the second electrode may have the samedimension. The term “dimension” refers to one or more of a width, alength, a surface area, and a shape of the first and the secondelectrodes. In particular, the first and the second electrodes may bedesigned with a non-structured electrode shape, such as a shape withoutstructures such as inlets, notches, etc. The shape of the electrodes maybe determined by a manufacturing process, such as a cutting process.Thus, the shape may be essentially rectangular, wherein the term“essentially rectangular” refers to that within tolerances ofmanufacturing deviations from a rectangular shape are possible.

The first electrode and the second electrode may be made of anon-corrosive and non-passivating material.

The first electrode may comprise at least one electrode conductive layerand at least one reagent coating in contact with the first electrodeconductive layer. The term “electrode conductive layer” refers to alayer with electrically conductive properties. The term “electricallyconductive” refers to an electric conductivity, typically given in S/mor 1/Ωm of at least 10° S/m, typically of at least 10³ S/m and, moretypically, of at least 10⁵ S/m. The first electrode conductive layer maycomprise at least one of: a metal layer, in particular a noble metallayer selected from the group consisting of palladium, silver or gold; aconductive carbon layer, in particular a carbon paste layer. However,other types of metals may be used in addition or alternatively. As usedherein, the term “paste” refers to an amorphous substance containing oneor more particulate components, such as one or more conductivecomponents and/or powders, as well as one or more binder materials, suchas one or more organic binder materials. Additionally or alternatively,the first electrode conductive layer may comprise an aluminum layer,such as a sputtered aluminum layer, combined with a conductive carbonpaste.

The first electrode conductive layer may be disposed on a firstelectrode carrier layer, typically a first electrode carrier foil. Inone embodiment, the first electrode carrier layer may be coated with aconductive carbon paste, typically homogenously. Alternatively, asoutlined above, the first electrode carrier layer may be coated, e.g.,with gold or gold on palladium, etc. The test element may be produced ina continuous tape manufacturing process. Thus, the coated layer may becoated as thin as possible such that a multi-layer winding up of thecontinuous tape on a reel in a manufacturing process is possible. Thefirst electrode may have a multi-layer setup. As used herein, the term“electrode carrier layer” refers to an element of the first electrodeonto which further layers or elements of the first electrode can beapplied. In general, the electrode carrier layer may have an arbitraryshape, such as a strip-shape. The first electrode carrier layer maycomprise a flexible substrate, such as a plastic material and/or alaminate material and/or a paper material and/or a ceramic material. Theelectrode carrier layer may comprise a foil, in particular a polymericfoil. The first electrode conductive layer may extend from a firstlongitudinal edge of the first electron carrier layer to a secondlongitudinal edge of the first electrode carrier layer. The firstelectrode conductive layer may fully cover the first electrode carrierlayer. Thus, a width of the first electrode conductive layer correspondsto a width of the first electrode carrier layer, wherein the term“width” of the first electrode carrier layer and the first electrodeconductive layer refers to a maximum extension perpendicular to anelongated test element direction. However, as will be outlined below,embodiments are typical, wherein a length of the first electrodeconductive layer may be different to a length of the first electrodecarrier layer, in particular such that a handle length of the firstelectrode conductive layer may be shorter than the length of the firstelectrode carrier layer such that a handle of the test element may beformed.

The reagent coating may comprise at least one reagent stripe coated ontothe first electrode conductive layer. In one embodiment, the reagentstripe may be coated onto the first electrode carrier layer. The reagentstripe material may comprise at least one detector substance to performan electrically detectable electrochemical detection reaction with theanalyte. The at least one detector substance may comprise one or moreenzymes, such as glucose oxidase (GOD) and/or glucose dehydrogenase(GDH), typically an enzyme which, by itself and/or in combination withother components of the detector substance, typically is adapted toperform an oxidation and/or reduction reaction with the at least oneanalyte to be detected. The reagent stripe material may further compriseone or more auxiliary components, such as one or more co-enzymes and/ormay comprise one or more mediators that may be adapted for an improvedcharge transfer from one component of the detection reaction to anothercomponent. The reagent stripe may be coated homogenously onto the firstelectrode conductive layer. The coating may be performed in a diecoating process in at least one coating device followed by a dryingprocess by running through at least one drier.

The second electrode may comprise at least one second electrodeconductive layer. The second electrode conductive layer may comprise atleast one of: a metal layer, typically a metal layer selected from thegroup consisting of palladium, silver or gold; a conductive carbonlayer, in particular a carbon paste layer. The second electrode mayfurther comprise Ag/AgCl, in particular an Ag/AgCl paste. The Ag/AgClpaste may be coated onto the second electrode conductive layer such thatan area coated with the Ag/AgCl paste may face the reagent coating ofthe first electrode conductive layer. The second electrode conductivelayer may be disposed on a second electrode carrier layer, typically asecond electrode carrier foil. The second electrode carrier foil may bedesigned as a cover foil of the test element. In one embodiment, thesecond electrode carrier layer may be coated with a silver layer, forexample, the second electrode carrier layer may be sputtered with asilver layer. The second electrode conductive layer may extend from afirst longitudinal edge of the second electrode carrier layer to asecond longitudinal edge of the second electrode carrier layer. Thesecond electrode conductive layer may fully cover the second electrodecarrier layer. Thus, a width of the second electrode conductive layercorresponds to a width of the second electrode carrier layer, whereinthe term “width” of the second electrode carrier layer and the secondelectrode conductive layer refers to a maximum extension perpendicularto an elongated test element direction.

The test element comprises at least one capillary capable of receiving asample of the body fluid. As used herein, the term “capillary” refers toan element which is adapted to receive the sample of the body fluidand/or transport the sample of the body fluid by capillary forces. Thecapillary element may comprise at least one volume configured to receivethe sample of the body fluid, e.g., one or more capillary caps and/orone or more capillary slots and/or one or more capillary tubes having anarbitrary cross-section, such as a rectangular cross-section and/or arounded cross-section and/or a polygonal cross-section.

The first electrode and the second electrode are arranged on opposingsides of the capillary. The first and the second electrode are arrangedas opposing electrodes, such that a surface of the first electrode facesa surface of the second electrode. The first electrode and the secondelectrode are arranged such that during a capillary filling the firstelectrode and the second electrode are wetted simultaneously and at anequal rate. An increment of a wetted surface area dA1 of the firstelectrode per increment dV of a filled volume of the capillary at alltimes may equal an increment of a wetted surface area dA2 of the secondelectrode. Consequently, as used herein, the term “wetting at an equalrate”, in this context, generally refers to the fact that dA1/dV=dA2/dV,i.e., that the ratios of the wetted surface area and the filled volumeare equal for both electrodes, at least after a time required forreaching an equilibrium state. The time dependency of the wetting,however, not necessarily is equal, i.e., the equation dA1/dt=dA2/dt maybe true for all times but may also not be true for all points in time.The first electrode and the second electrode may be aligned in parallel,in particular as surfaces that are parallel to each other at least inthe direction defined by the length of the capillary. Further, asoutlined above, the first and the second electrode may have the samedimensions and may have a non-structured shape. The first electrode mayextend over a full length of the capillary. The second electrode mayextend over a full length of the capillary. As used herein, the term“length of the capillary” refers to a maximum extension of the capillaryin one dimension within the test element. In one embodiment, thecapillary may extend perpendicular to the elongated test elementdirection such that in this case the length of the capillary refers to amaximum extension of the capillary perpendicular to the elongated testelement direction. In an alternative embodiment, the capillary mayextend along the elongated test element direction such that in this casethe length of the capillary refers to a maximum extension of thecapillary along the elongated test element direction.

The first electrode and the second electrode are arranged such thatduring a capillary filling the first electrode and the second electrodeare wetted simultaneously. An increment of a wetted surface area dA1 ofthe first electrode per increment dV of a filled volume of the capillaryat all times may equal an increment of a wetted surface area dA2 of thesecond electrode. As used herein, the term “capillary filling” refers toa process of receiving the sample of the body fluid.

The first electrode and the second electrode and the capillary inbetween the first electrode and the second electrode form anelectrochemical cell, wherein the test element is configured to detectthe at least one analyte independently of a filling level of theelectrochemical cell. The electrochemical cell may extend over the fulllength of the capillary. Hence, the first electrode and the secondelectrode may extend over the full length of the capillary.

The sample of the body fluid may be applicable to one or more of: a sidedose position, a top dose position, and a front dose position. As usedherein, the term “side dose position” refers to a position on anelongated edge of the test element where the sample of the body fluid isapplicable, e.g., the test element may comprise at least two opposingopenings at edges of the test element. A side dose position may be anideal application position for capillary blood from a finger stick. Asused herein, the term “top dose position” refers to a position where thesample of the body fluid can be applied from above through a layerset-up of the test element into the capillary. The test element maycomprise a top dose position and further a through hole extendingthrough a cover foil into the capillary. As used herein, the term “coverfoil” refers to an element of the test element confining a layer setupof the test element, e.g., a top foil. The cover foil may be configuredas the first electrode carrier layer or the second electrode carrierlayer. The through hole may be positioned such that the through hole maytouch the capillary at one edge of at least one capillary wall. A topdose position may be an ideal application position for dosing the samplewith a transfer device, e.g., a pipette. Further, in case the testelement comprises at least one top dose position, it may be possible toclose the capillary on all sides if an appropriate venting of thecapillary space is possible, e.g., via a venting element, e.g., a smallvent hole opening or a venting membrane. As used herein, the term “frontdose position” refers to a position at a front face of the test element,wherein the term “front face” refers to a front surface area of a widthof the test element. For example, the front dose position may be an openside at the front face. The side dose position, the top dose positionand the front dose position may be positioned at a distance to a regionof the test element inserted into a further measurement device, e.g., ameter, such that no sample is transferred into the further measurementdevice. This is advantageous under hygienic aspects and cleaning anddisinfection requirements.

The test element may have an elongated shape extending along alongitudinal axis, wherein the capillary at least partially extendsalong the longitudinal axis of the test element. The term “at leastpartially extending along the longitudinal axis” refers to embodimentswherein the capillary may fully extend along the longitudinal axisand/or embodiments wherein parts of the capillary may not extend alongthe longitudinal axis. In particular, this embodiment may be used iftesting times significantly longer than a minute, e.g., testing times ofmore than 5 minutes, are required, because the sample within thecapillary will not dry off. Further, this embodiment may be used in casethe sample has to be transported to a further device, e.g., to a heatingdevice, typically a thermostatic controlled heating device within themeter, in case test parameters might need to be heated up to atemperature above the surrounding temperature. The test element maycomprise a region insertable into the further device. The capillary maycomprise a vent hole opening, such as a vent hole opening at an end ofthe capillary in the direction of the insertable region. In thisembodiment, the first electrode may comprise a second reagent coating inthe direction of the insertable region, which may create a hydrophobicsurface. The hydrophobic surface may hinder the passage of the sample ofthe body fluid up to the vent hole, and thus contaminate the furtherdevice. To ensure a reliable and quick sample transport, in general,capillary walls may be hydrophilic. Thus, surfaces of the capillarywalls may be treated with at least one detergent and/or with at leastone surfactant, in particular the surfaces of the first electrode andthe second electrode, which are arranged on opposing sides of thecapillary.

The test element may have an elongated shape extending along alongitudinal axis, wherein the capillary at least partially extendsperpendicular to the longitudinal axis. The term “at least partiallyextending perpendicular to the longitudinal axis” refers to embodimentswherein the capillary may fully extend perpendicular to the longitudinalaxis and/or embodiments wherein parts of the capillary may not extendperpendicular to the longitudinal axis. The capillary may extend from afirst opening at a first longitudinal edge of the test element to asecond opening at a second longitudinal edge of the test element. Thecapillary may have an open side at a front face of the test element. Thetest element may have a front dose position located at the front face ofthe test element. The capillary may comprise a vent hole.

The test element may comprise a side dose position located on one orboth of the first opening or the second opening. In one embodiment, thecapillary may be open at three sides. The capillary may comprise threeopenings for receiving the sample of the body fluid, for example, thecapillary can receive the sample from at least two side dose positionssuch as opposing openings of the capillary on opposing edges of the testelement, and a third dose position such as a top opening or a frontopening. If the test element comprises a side dose position and,therefore, a first opening and the second opening, one of these openingsmay be used for sample dosing and the other opening has the function ofa vent hole opening. In this embodiment, no separate vent hole openingis necessary.

At least one wall of the test element located outside the capillary butnext to the opening for receiving the sample of the body fluid may be atleast partially coated by at least one hydrophobic coating. Thehydrophobic coating may avoid an outspreading of the sample of the bodyfluid outside the capillary and therefore may support the filling of thecapillary. For example, a hydrophobic coating may be applied on top ofthe second electrode carrier layer, e.g., at the top dose position,and/or in front of the first electrode carrier layer.

The test element may comprise a strip handle. As used herein, the term“strip handle” refers to an element of the test element configured toavoid getting in contact with the sample of the body fluid, such as whenhandling the test element, e.g., when taking the test element out of astorage vial, inserting the test element into the further device, orpulling out the test element from the further device. The test elementmay comprise a layer setup disposed on top of at least one carrierelement, wherein the carrier element, in a longitudinal direction of thetest element, protrudes from the layer setup, thereby forming the striphandle.

The test element may comprise at least one carrier element. As usedherein, the term “carrier element” refers to an arbitrary elementcomprising one or more components. The carrier element may be adapted tocarry other components of the test element, such as the at least onetest field. Thus, the carrier element may comprise a single-layer set-upof a multi-layer set-up, such as a laminate set-up. The carrier elementmay comprise one or more materials, such as plastic materials, and/orpaper materials, and/or cardboard-materials, and/or ceramic materials.Most typically, the carrier element may comprise a flexible substrate,e.g., one or more plastic materials selected from the group consistingof: a polycarbonate, a polyethylene, a polyethylene terephthalate, andan acrylonitrile-butadiene-styrene. However, in addition oralternatively, other plastic materials are applicable. Additionally oralternatively, the carrier element may comprise one or more metallicmaterials such as aluminum. Further, combinations of materials arepossible, such as laminate materials, wherein the combinations maycomprise two or more different types of materials, such as a combinationof plastic materials and metallic materials, such as in a layer setup.In general, the carrier element may have an arbitrary shape, such as astrip-shape. The at least one carrier foil may be a polymer foil. The atleast one carrier foil may be configured to provide a stability of thetest element.

The test element may comprise a first electrode contact zone and asecond electrode contact zone configured to contact the first electrodeand the second electrode with the further device, in particular a meter.In one embodiment, the first electrode contact zone and the secondelectrode contact zone may be configured to be electrically contactedfrom the same side of the test element. The first electrode contact zoneand the second electrode contact zone may be arranged in differentlayers of a layer setup of the test element, wherein one of the firstelectrode contact zone and the second electrode contact zone mayprotrude over the other one of the first electrode contact zone and thesecond electrode contact zone. The first electrode contact zone and thesecond electrode contact zone may form different steps of a staircaseconfiguration of the layer setup. For example, the first electrodecontact zone and the second electrode contact zone may be tworectangular zones at one end of the test element. The first and secondelectrode contact zones may each be hit upon by at least one connectorof the further device, e.g., meter connector pins. The further devicemay have two pairs of connectors, one pair for each of the first and thesecond electrode. One connector of each connector pair may be configuredto support a current flow through the test element. The other connectormay be used to detect a voltage. Such a configuration, also called4-wire-technique, may allow an electronic controller of the furtherdevice to compensate voltage drop induced by parasitic transferresistances at connection spots of the first and second electrodecontact zones and the connectors. However, as the first electrode andthe second electrode may be configured as opposing electrodes, to allowan electrical contact from the same side of the test element, the firstelectrode or the second electrode may be electrically contacted by atleast one electrically conductive turnover element, as will be outlinedin detail below.

In one embodiment, the first electrode contact zone and the secondelectrode contact zone may be configured to be electrically contactedfrom opposing sides of the test element. The first electrode may becontacted through the first electrode contact zone protruding out of thetest element layer setup. A punched hole through the cover foil and thespacer foil may be configured as the second electrode contact zone, inparticular a contact hole. Thus, no additional electrically conductiveturnover element may be required as for the same side contact asoutlined above. The first and second electrode contact zones may be hitupon by the at least one connector of the further device, e.g., meterconnector pins. Typically, the further device may have two pairs ofconnectors, one pair for each of the first and the second electrode. Onepair of connectors may contact one of the first or second electrodesfrom one side of the test element, whereas the other pair may contactthe other one of the first or second electrode from an opposing side ofthe test element.

One or both of the first electrode or the second electrode may beelectrically contacted by at least one electrically conductive turnoverelement, wherein the first or second electrode, respectively, may beoriented to face a first direction, wherein the electrically conductiveturnover element may be contactable from a second direction, the seconddirection being an opposite direction of the first direction. Theelectrically conductive turnover element may comprise at least one of anelectrically conductive layer or an electrically conductive foil havinga first section and a second section, the first section electricallycontacting the first or second electrode, respectively, and the secondsection being electrically contactable. For example, the electricallyconductive turnover element may be configured as a conductive adhesivelayer. The electrically conductive turnover element may be partiallycovered by at least one layer comprising the first or second electrode,respectively, wherein the second section may be located in an uncoveredregion. As used herein, the term “partially covered” refers to thatparts of the electrically conductive turnover element may be covered bythe at least one layer comprising the first or second electrode andparts of the electrically conductive turnover element may be uncovered.The electrically conductive turnover element may be laminated to thefirst or second electrode, respectively.

The test element may comprise a layer setup, wherein the first electrodemay comprise at least one first electrode conductive layer disposed onat least one first electrode carrier layer, wherein the second electrodemay comprise at least one second electrode conductive layer disposed onat least one second electrode carrier layer. The layer setup may bearranged such that the first electrode conductive layer faces the secondelectrode conductive layer, with the capillary in between. At least onespacer layer may be disposed in between the first electrode conductivelayer and the second electrode conductive layer. Further, the layersetup may comprise at least one adhesive layer. A height of theelectrochemical cell may be defined by a thickness of the spacer layerand of adhesive layers in between the first and second electrode.Embodiments are feasible, wherein the at least one adhesive layer may bearranged between the carrier element and the first electrode carrierlayer, and/or between the reagent coating and the spacer layer. Forexample, in case the at least one adhesive layer may be arranged betweenthe carrier element and the first electrode carrier layer, the at leastone adhesive layer may be positioned such that a region defined by aposition of the electrochemical cell is not covered by the adhesivelayer such that a gap between the carrier element and the firstelectrode may be formed. Thus, in case a user may inadvertently bend thetest element, a distance between the first and the second electrodesurfaces may remain unaffected. Further, the at least one adhesive layermay be a conductive adhesive layer, e.g., a silver-based adhesive, whichmay be arranged between the cover foil and the second electrodeconductive layer and/or the second electrode conductive layer and thespacer layer. However, other arrangements of adhesive layers may befeasible.

The test element may comprise a layer setup. The working electrode maycomprise at least one first electrode conductive layer. The firstelectrode conductive layer may comprise a carbon ink coating. The firstelectrode conductive layer may be disposed on at least one firstelectrode carrier layer. The first electrode carrier layer may be afoil, e.g., a top foil. The working electrode may comprise at least onereagent coating, e.g., a detection reagent coating, in contact with thefirst electrode conductive layer. The reagent coating may cover at leastpartially the first electrode conductive layer. The counter electrodemay comprise at least one second electrode conductive layer. The secondelectrode conductive layer may comprise a carbon ink coating. The secondelectrode conductive layer may be disposed on at least one secondelectrode carrier layer. The second electrode carrier layer may be afoil, e.g., a bottom foil. The counter electrode may comprise at leastone reagent coating in contact with the second electrode conductivelayer. The reagent coating may comprise a redox chemistry. The reagentcoating may comprise an Ag/AgCl ink. The reagent coating may cover atleast partially the second electrode conductive layer. The reagentcoating of the working electrode and the counter electrode may coverequal areas of the respective electrode conductive layers. At least onespacer layer may be disposed in between the first electrode conductivelayer and the second electrode conductive layer. Adhesive layers may beapplied to one or both sides of the spacer layer. Thus, the firstelectrode conductive layer and the second electrode conductive layer maybe fixed within the layer setup by the spacer layer. The first electrodeand the second electrode and the capillary in between the firstelectrode and the second electrode form an electrochemical cell. Theelectrochemical cell may extend over the full length of the capillary.The first electrode and the second electrode may extend over the fulllength of the capillary. The spacer layer may be arranged such that itdoes not extend over the full length of the test element. For example,the spacer layer may cover the capillary partly. The capillary may beopen at three sides. The sample of bodily fluid may be applicable to aside dose position and a front dose position.

Further, the test element may comprise a first electrode contact zoneand a second electrode contact zone configured to contact the workingelectrode and the counter electrode with a further device. The firstelectrode contact zone and/or the second electrode contact zone, and theside and front dose positions, may be arranged at opposing ends of thetest element. The first electrode contact zone and the second electrodecontact zone may be arranged in different layers of the layer setup ofthe test element. The first electrode contact zone and the secondelectrode contact zone may be configured to be electrically contactedfrom opposing sides of the test element, for example, at top and atbottom sides of the test element. The first electrode conductive layerand the first electrode carrier layer may form an overhang on thecontact side of the test element over the second electrode conductivelayer and the second electrode carrier layer. Thus, parts of the firstelectrode conductive layer may be exposed and may allow contacting theworking electrode with the further device. As described above, thespacer layer may be arranged such that it does not extend over the fulllength of the test element. The spacer layer may comprise at least onehole and/or at least one recess, which may have an arbitrary form, forexample circular or rectangular. The spacer layer may be formed in onepart or in multiple parts. The second electrode contact zone may beformed in the following way: The first electrode conductive layer andthe first electrode carrier layer may comprise at least one hole and/orat least one recess, which may have an arbitrary form, for examplecircular or rectangular. For example, the at least one recess in thefirst electrode conductive layer and the first electrode carrier layermay be formed by cutting and/or punching. The spacer layer may bearranged such that, within the layer setup of the test element, thespacer layer may not cover the at least one hole and/or at least onerecess of the first electrode conductive layer and the first electrodecarrier layer. For example, the at least one recess in the spacer layermay be formed by cutting and/or punching. Thus, parts of the secondelectrode conductive layer may be exposed and may allow contacting thecounter electrode with the further device.

In accordance with another embodiment of the present disclosure, amethod for producing a test element, disclosed in one or more of theembodiments above or disclosed in further detail below, is disclosed.The method comprises at least one step of forming a layer setup. Thefirst electrode, the second electrode and the capillary are formed suchthat the first electrode and the second electrode are arranged onopposing sides of the capillary. For a description of possibleembodiments and definitions of the test element, reference can be madeto the above-mentioned test element according to the present disclosure.

The method may comprise the method steps disclosed in further detailbelow. The method steps, as an example, may be performed in the givenorder. However, a different order is also feasible. Further, one or moreor even all of the method steps may be performed in parallel or in atimely overlapping fashion. Further, one or more or even all of themethod steps may be performed once or repeatedly.

In a particular embodiment, the test element may be a test strip, e.g.,the test element has a strip-shape, in particular a rectangular basearea.

The test element may be produced in a continuous process. As usedherein, the term “continuous process” refers to an arbitrary process inwhich, by contrast with batch-to-batch processes, production proceedssuccessively and without interruption of a supporting tape, e.g., acarrier tape. The continuous process may be a reel-to-reel process. Forexample, the supporting tape may be provided from a starting roller andmay be wound up onto a further roller after laminating further tapesonto it.

The step of forming the layer setup may comprise at least one laminationstep, wherein in the lamination step at least two layers are combined bya lamination process. The lamination step may comprise a lamination ofat least two tapes. The layer setup may comprise the above describedelements of the test elements such as one or more of the carrierelement, the first electrode, the second electrode, the spacer layer,and at least one adhesive layer.

The method further may comprise cutting the layer setup into teststrips. The layer setup may be a tape-shaped layer setup, wherein awidth of the tape-shaped layer setup defines a length of the teststrips. The length of the test strip may be understood as maximumextension of the test trip in an elongated direction. The width of thelaminated tapes may be understood as maximum extension in a dimensionperpendicular to a tape elongation direction, wherein in the tapeelongation direction the extension of the tape exceeds an extensionperpendicular to a tape elongation direction, typically by at least afactor of 3, at least a factor of 10, or even at least a factor of 100.The term “cutting” may be understood as dividing the laminated tape intoseparated test strips, such that the separated test strips may be usedindividually. The layer setup, e.g., the laminated tape, may have alength allowing for cutting several test strips, typically 10 or more,more typically 20 or more, and most typically 50 test strips or more,from one tape. The cutting may be performed by a cutting device. Such astrip design made from an endless unstructured tape may be advantageousbecause the strip length and width can easily be adapted by changing thecutting distance and lamination tape widths.

The forming of the capillary may comprise cutting out the capillary fromat least one spacer. The cutting may comprise a kiss-cut process. In thekiss-cut process, a cutting profile wheel may be used. The spacer, inparticular a spacer tape forming after cutting the spacer layer of thetest element, may be covered on both sides with one or both of anadhesive and a release liner. The spacer may run through a gap betweentwo contrary rotating wheels, where one wheel is the cutting profilewheel such that an outlined capillary shape may be cut into the spacer.The strip width may be defined by a distance between two cut capillarystructures.

The working electrode may comprise at least one reagent, wherein themethod may comprise coating a reagent stripe onto at least one carrierlayer. The coating may comprise a die coating process. The die coatingfurther may comprise running the reagent stripe through a drierfollowing a coating device.

The supporting tape, e.g., a carrier layer, may be provided, inparticular as a polymer foil. On top of the carrier layer, a firstelectrode carrier layer is laminated. The first electrode carrier layermay be coated with a conductive layer. The first electrode carrier layermay have a smaller width than a width of the supporting tape such that,when laminating the coated electrode carrier layer and the supportingtape, the strip handle may be formed. The spacer layer may be laminatedonto the coated first electrode carrier layer. The spacer layer may havea width smaller than the coated first electrode carrier layer. Thespacer layer may be laminated onto the coated first electrode carrierlayer such that on both edges of the coated first electrode carrierlayer a part may be uncovered from the spacer layer, forming anelectrode contact zone. The spacer layer may be coated with a conductivematerial, typically sputtered with a thin silver layer. Onto the spacerlayer a conductive adhesive layer may be laminated, such that the firstand second electrode contact zones may be uncovered. On top of theconductive adhesive layer, the second electrode carrier layer may belaminated, which may be coated with a thin silver layer, which maycoated by a stripe of an Ag/AgCl paste. The stripe may be positionedsuch that it faces the first electrode reagent layer. Finally, the layersetup may be cut such that the capillary is open at three sides.

Further, the method may comprise creating holes in the test element,e.g., holes for a top dose position, a contact hole, and a vent holeopening. In general, the holes may have an arbitrary shape, e.g., arectangular shape or a round shape.

In accordance with yet another embodiment of the present disclosure, asystem for determining at least one property of a sample is disclosed.The system comprises at least one test element, disclosed in one or moreof the embodiments above or disclosed in further detail below. Thesystem further comprises at least one measurement device adapted forperforming at least one electrical measurement using the test element.For a description of possible embodiments and definitions of the testelement, reference can be made to the above-mentioned test elementaccording to the present disclosure.

As used herein, the term “determining at least one property” refers todetecting at least one analyte in a bodily fluid. However, embodimentswherein other properties may be detected are feasible. As used herein,the term “measurement device” refers to an arbitrary device, typicallyan electronic device, which may be handled independently from the testelement. The measurement device may be adapted to interact with the testelement in order to detect the at least one signal produced by one ofthe first and second electrode and to apply a voltage to the other oneof the first and second electrode. The measurement device further may beadapted to derive at least one item of information regarding thepresence and/or concentration of the analyte in the body fluid from thisdetection. Thus, the measurement device may comprise at least oneelectronic evaluation device interacting with the first and secondelectrodes, in order to derive the at least one information and/orconcentration of the at least one analyte from the at least one signal.Thus, the measurement device may comprise at least one evaluation unitcomprising at least one data processing device, such as amicrocontroller.

The test element may be inserted into a test element receptacle of themeasurement device. As used herein, a test element receptacle may be amechanical interface adapted to receive the at least one test element.Most typically, the test element receptacle is a test element receptacleadapted to receive precisely one test element at a time. The mechanicalinterface may be adapted to at least partially receive the test elementand to mechanically secure the test element during measurement. The testelement receptacle may be configured to contact the first electrode andthe second electrode electrically, in particular via contact of thefirst and second electrode contact zones with at least one connectorelement of the measurement device, e.g., two pairs of connector pins.

The measurement device may be configured to perform at least oneimpedance measurement using the first electrode and the secondelectrode. The measurement device may be further configured to performat least one amperometric measurement using the first electrode and thesecond electrode.

The measurement device may be configured to detect both an AC signal anda DC signal. The measurement device may be configured to detect the ACsignal and DC signal simultaneously. A parallel determination of boththe AC signal and DC signal may be performed by overlapping respectiveexcitation potentials. The measurement device may be configured todetect the AC signal and the DC signal sequentially. The time intervalbetween two measurements may be as short as possible to minimizetime-dependent effects. The measurement device may be configured toapply an AC signal to the first electrode and the second electrode andto detect, e.g., continuously, a response. The measurement device maydetect a contact time, e.g., a time when the sample may be in contactwith the first and second electrode surfaces, by applying the AC signalbetween the first and the second electrode and measuring the responseover time. In case the AC response may exceed a predefined threshold,this may be recognized as “sample dosing detected”.

The measurement device is configured to detect the at least one analyteindependently of a filling level of the electrochemical cell. Byperforming a simultaneous AC- and DC-measurement a complete filling ofthe capillary of the test element may not be necessary. The AC signalmay be proportional to the filling level of the capillary. Theelectro-conductivity G of the electrochemical cell may be proportionalto the filling level of the capillary and is defined as:

G=x·(l·w)/h,

wherein x is a specific conductivity of a sample, l is the filled lengthof the capillary, w is the width of the capillary and h is the height ofthe capillary. As described above the height of the electrochemical cellmay be defined by a thickness of the spacer layer and of adhesive layersin between the first and second electrode. Further as described above,the term “length of the capillary” refers to a maximum extension of thecapillary in one dimension within the test element. In one embodiment,the capillary may extend perpendicular to the elongated test elementdirection such that in this case the length of the capillary refers to amaximum extension of the capillary perpendicular to the elongated testelement direction. In an embodiment, the capillary may extend along theelongated test element direction such that in this case the length ofthe capillary refers to a maximum extension of the capillary along theelongated test element direction. The term “filled length of thecapillary” refers to an amount of the whole capillary length, which isfilled by the sample. The term “width” of the capillary refers, in a twodimensional space, to a maximum extension of the capillary in adimension perpendicular to the length of the capillary.

The amperometric response DC of the electrochemical cell may beproportional to the filling level of the capillary and is defined by theso-called Cottrell function:

DC=(l·w)·c·F·z·D ^(1/2) ·t ^(1/2),

wherein F is the Faraday constant, c the initial concentration of theanalyte, z the number of transferred electrons, D the diffusioncoefficient, and t the measuring time.

Both the electro-conductivity and the amperometric response typicallyare proportional to the filling level of the capillary such that therelation, e.g., the ratio, of AC and DC measurement value is independentfrom the filling level. Variations in the filling level and/or effectsdue to the filling level may be compensated by calibration. Thus, byperforming a simultaneous AC- and DC-measurement the test element may bedesigned without additional dose or fill detect electrodes.

The measurement device may be further configured to electrically monitora filling process of the capillary. For example, in an embodimentwherein the capillary at least partially may extend along thelongitudinal axis of the test element, the measurement device may beconfigured to electrically monitor when the sample may reach the reagentcoating of the working electrode. The reagent coating may comprise atleast one redox active substance, which may be oxidized or reduced atthe first electrode surface. The measurement device may be configured toapply a DC voltage between the first and the second electrode and todetect a response, in particular a DC response. The sample may start todissolve the reagent and in case the DC voltage is applied, the DCresponse, in particular a response signal, may increase. In case the DCresponse may exceed a predefined threshold, this may be recognized as“analyte detection started”. If the time for reaching the reagentcoating may exceed a predefined limit, an error message may be generatedby the measurement device.

Further, the measurement device may be configured to electricallymonitor when the capillary may be filled completely. Thus, after “sampledosing detected” and/or “analyte detection started” was detected, asecond AC voltage may be applied to the electrodes and the response maybe detected. If the detected response signal may reach a steady state,this may be recognized as filled. If the time for filling may exceed apredefined limit, an error message may be generated by the measurementdevice. A gradient of the response signal may be measured. If thegradient amounts or exceeds a predefined threshold, this may berecognized as filled. The predefined threshold may be chosen such that aminimum filling level is ensured. The predefined threshold may be chosenwith respect to a specific conductivity of a sample. The predefinedthreshold may be chosen with respect to the sample having the lowestexpected specific conductivity. Additional predefined thresholds may beassigned to different values of the gradient of the response signal suchthat the filling level can be determined and monitored.

The measurement device may be configured to perform at least one initialfailsafe measurement before applying the sample of the bodily fluid. Thefailsafe measurement may comprise at least one electrical measurementusing the first electrode and the second electrode. The electricalmeasurement may be used for deriving at least one electrical measurementvalue, wherein the failsafe measurement may further comprise comparingthe electrical measurement value with at least one threshold value. Thefailsafe measurement may comprise detecting at least one damage and/ordeterioration of the at least one of the first electrode or the secondelectrode.

In accordance with still another embodiment of the present disclosure, amethod for determining at least one property of a sample is disclosed.As outlined above, the term “determining at least one property” refersto detecting at least one analyte in a bodily fluid. With respect todefinitions and embodiments reference can be made to definitions andembodiments of a test element, measurement device and a method forproducing a test element as disclosed above. In the method, a system fordetermining at least one property of a sample is used. With respect todefinitions and embodiments of the system, reference can be made to theabove-mentioned system according to the present disclosure. The methodcomprises the following steps:

-   -   a) Connecting the test element to at least one measurement        device;    -   b) Applying a sample of bodily fluid to a capillary of at least        one test element;    -   c) Determining both an AC signal and a DC signal; and    -   d) Calibrating measurement results by using the AC and DC        signal.

The method steps, as an example, may be performed in the given order.However, a different order is also feasible. Further, one or more oreven all of the method steps may be performed in parallel or in a timelyoverlapping fashion. Further, one or more or even all of the methodsteps may be performed once or repeatedly. With respect to definitionsand embodiments of the test element, capillary and measurement device,reference can be made to definitions and embodiments of the testelement, capillary and the measurement system as given above.

In step a) a sample of bodily fluid is applied to a capillary of atleast one test element. As used herein, the term “applying” refers to aprocess of contacting the sample with the test element such that afilling of the capillary is possible and to a process of filling thecapillary. The sample of the body fluid may be applicable to one or moreof: a side dose position, a top dose position, and a front doseposition. The sample may be applied to the test element by a side doseposition, e.g., capillary blood from a finger stick may be applied tothe side dose position by pressing the finger to the side dose position.The sample of the body fluid may be applied from above through a layerset-up of the test element into the capillary, for example by a transferdevice, e.g., a pipette. The sample may be applied to the test elementby a front dose position.

As used herein, the term “connecting the test element to at least onemeasurement device” refers to inserting the test element into a testelement receptacle of the measurement device, e.g., a mechanicalinterface, and electrically contacting the first electrode and thesecond electrode, in particular via contact of the first and secondelectrode contact zones with at least one connector element of themeasurement device, e.g., two pairs of connector pins.

For a stable amperometric measurement of the at least one property of asample, e.g., the concentration of glucose in bodily fluid, it may benecessary that the capillary is filled completely before the measurementstarts. In principle, filling of a capillary may be determined byadditional electrodes such as dose or fill detect electrodes. Renouncingthe use of additional electrodes may reduce manufacturing costs andmaterial costs of the test element. The disclosed method permitsdetermining the at least one property of a sample without effects and/orinfluences of the capillary filling without using additional electrodes.In particular, a complete filling of the capillary may be not necessary.In step c) both an AC signal and a DC signal are determined. As usedherein, the term “determining both an AC signal and a DC signal” refersto both of an AC and DC excitation, e.g., a parallel AC and DCexcitation, and a detection of both of AC and DC response signals. TheAC response signal may be or may be proportional to the electroconductivity of the electrochemical cell. The AC signal and the DCsignal may be determined simultaneously or sequentially. Thedetermination of the AC and DC signal may be performed by overlappingexcitation potentials.

In step d) the measurement results are calibrated by using the AC and DCsignal. As used herein, the term “calibration” refers to reducing,typically eliminating, an influence and/or an impact of the fillinglevel of the capillary to the AC response signal and/or DC responsesignal. Both the AC signal and the DC signal may be proportional to thefilling level of the capillary such that effects due to a filling of thecapillary are compensated. The AC response signal may be or may beproportional to the electro-conductivity of the electrochemical cell.The electro-conductivity G of the electrochemical cell may beproportional to the filling level of the capillary and is defined as:

G=x·(l·w)/h,

wherein x is a specific conductivity of a sample, l is the filled lengthof the capillary, w is the width of the capillary, and h is the heightof the capillary. The DC response signal may be or may be proportionalto the amperometric response DC of the electrochemical cell, which isdefined by the so-called Cottrell function:

DC=(l·w)·c·F·z·D ^(1/2) ·t ^(1/2),

wherein F is the Faraday constant, c the initial concentration of theanalyte, z the number of transferred electrons, D the diffusioncoefficient, and t the measuring time. Thus, both of the AC responsesignal and the DC response signal may be proportional to the filledlength of the capillary. By measuring AC and DC signal simultaneously,effects due to varying filling level may be compensated. The determinedvalues of electro-conductivity G and the amperometric response DC may becombined. Effects due to varying filling levels of the capillary may becompensation by a suitable calibration. For example, a ratio of theelectro-conductivity G and the amperometric response may be used. Thus,the fraction may be reduced by the filled length of the capillary.Consequently, the method, specifically method step d), may imply forminga ratio, such as a ratio of G and the DC response signal and/or a ratioof the AC response signal and the DC response signal, wherein the ratiois independent from the filling length 1, i.e., independent from thefilling level of the electrochemical cell, e.g., under constanttemperature conditions and other measurement conditions.

The method may further comprise determining a contact time, wherein anAC signal may be applied between at least one first electrode and atleast one second electrode of the test element. A response over time maybe measured, for example an AC response signal may be detected. As usedherein, the term “contact time” refers to a time when the sample may bein contact with the first and second electrode surfaces. The AC responsemay be compared to a predefined threshold. In case the AC response mayexceed a predefined threshold, this may be recognized as “sample dosingdetected”.

The method may further comprise determining a filling level of thecapillary, wherein an AC signal may be applied between the at least onefirst electrode and the at least one second electrode of the testelement, and wherein a response signal over time may be measured,wherein the response may be compared to at least one predefinedthreshold. As used herein, the term “determining a filling level of thecapillary” may generally refer to an arbitrary process of generating atleast one item of information on a filling of the capillary. Thus, theat least one item of information may, as an example, comprise an item ofinformation on whether the filling level is above or below at least onepredetermined or determinable threshold, as will be explained in furtherdetail below. Additionally or alternatively, however, one or more otheritems of information on the filling may be determined.

For example, after “sample dosing detected” and/or “analyte detectionstarted” was detected, a second AC voltage may be applied to theelectrodes. If the detected response signal may reach a steady state,this may be recognized as filled. If the time for filling may exceed apredefined limit, an error message may be generated by the measurementdevice. A gradient of the response signal may be measured. If thegradient amounts or exceeds the predefined threshold, this may berecognized as filled. The predefined threshold may be chosen such that aminimum filling level is ensured. The predefined threshold may be chosenwith respect to a specific conductivity of a sample. The predefinedthreshold may be chosen with respect to the sample having the lowestexpected specific conductivity. Additional predefined thresholds may beassigned to different values of the gradient of the response signal suchthat the filling level can be determined and monitored.

The method may further comprise monitoring a filling process of thecapillary, wherein a DC voltage may be applied between the firstelectrode and the second electrode. A DC response may be detected. TheDC response may be compared to a predefined limit. When the sample mayreach the reagent coating of the working electrode, the reagent coating,which may comprise at least one redox active substance, may be oxidizedor reduced at the first electrode surface. A DC voltage may be appliedbetween the first and the second electrode and the response, inparticular a DC response, may be detected. The sample may start todissolve the reagent and in case the DC voltage is applied, the DCresponse, in particular a response signal, may increase. In case the DCresponse may exceed a predefined threshold, this may be recognized as“analyte detection started”. If the time for reaching the reagentcoating may exceed a predefined limit, an error message may be generatedby the measurement device.

Summarizing the findings of the present disclosure, the followingembodiments are typical:

Embodiment 1

A test element for electrochemically detecting at least one analyte in abodily fluid, wherein the test element comprises at least one firstelectrode and at least one second electrode, wherein the first electrodeis designed as a working electrode and the second electrode is designedas a counter electrode, wherein the test element comprises at least onecapillary capable of receiving a sample of the body fluid, wherein thefirst electrode and the second electrode are arranged on opposing sidesof the capillary, wherein the first electrode and the second electrodeand the capillary in between the first electrode and the secondelectrode form an electrochemical cell, wherein the test element isconfigured to detect the at least one analyte independently of a fillinglevel of the electrochemical cell, wherein the first electrode and thesecond electrode are arranged such that during a capillary filling thefirst electrode and the second electrode are wetted simultaneously andat an equal rate.

Embodiment 2

The test element according to the preceding embodiment, wherein thefirst electrode extends over a full length of the capillary.

Embodiment 3

The test element according to any one of the preceding embodiments,wherein the second electrode extends over a full length of thecapillary.

Embodiment 4

The test element according to any one of the preceding embodiments,wherein an increment of a wetted surface area dA1 of the first electrodeper increment dV of a filled volume of the capillary at all times equalsan increment of a wetted surface area dA2 of the second electrode.

Embodiment 5

The test element according to any one of the preceding embodiments,wherein at least one wall of the test element located outside thecapillary but next to the opening for receiving the sample of the bodyfluid is at least partially covered by at least one hydrophobic coating.

Embodiment 6

The test element according to the preceding embodiment, wherein theelectrochemical cell extends over the full length of the capillary.

Embodiment 7

The test element according to any one of the preceding embodiments,wherein the first electrode and the second electrode are made of anon-corrosive and non-passivating material.

Embodiment 8

The test element according to any one of the preceding embodiments,wherein a surface area of the first electrode and a surface area of thesecond electrode forming the electrochemical cell have the samedimension.

Embodiment 9

The test element according to any one of the preceding embodiments,wherein the first electrode comprises at least one first electrodeconductive layer and at least one reagent coating in contact with thefirst electrode conductive layer.

Embodiment 10

The test element according to the preceding embodiment, wherein thefirst electrode conductive layer comprises at least one of: a metallayer, typically a noble metal layer selected from the group consistingof palladium, platinum, silver or gold; a conductive carbon layer, inparticular a carbon paste layer.

Embodiment 11

The test element according to any one of the two preceding embodiments,wherein the first electrode conductive layer is disposed on a firstelectrode carrier layer, typically a first electrode carrier foil.

Embodiment 12

The test element according to the preceding embodiment, wherein thefirst electrode conductive layer extends from a first longitudinal edgeof the first electrode carrier layer to a second longitudinal edge ofthe first electrode carrier layer.

Embodiment 13

The test element according to the preceding embodiment, wherein thefirst electrode conductive layer fully covers the first electrodecarrier layer.

Embodiment 14

The test element according to any one of the five preceding embodiments,wherein the reagent coating comprises at least one reagent stripe coatedonto the first electrode conductive layer.

Embodiment 15

The test element according to any one of the preceding embodiments,wherein the second electrode comprises at least one second electrodeconductive layer.

Embodiment 16

The test element according to the preceding embodiment, wherein thesecond electrode conductive layer comprises at least one of: a metallayer, typically a noble metal layer selected from the group consistingof palladium, platinum, silver or gold; a conductive carbon layer, inparticular a carbon paste layer.

Embodiment 17

The test element according to any one of the two preceding embodiments,wherein the second electrode further comprises Ag/AgCl, in particular anAg/AgCl paste.

Embodiment 18

The test element according to any one of the three precedingembodiments, wherein the second electrode conductive layer is disposedon a second electrode carrier layer, typically a second electrodecarrier foil.

Embodiment 19

Test element according to the preceding embodiment, wherein the secondelectrode conductive layer extends from a first longitudinal edge of thesecond electrode carrier layer to a second longitudinal edge of thesecond electrode carrier layer.

Embodiment 20

The test element according to the preceding embodiment, wherein thesecond electrode conductive layer fully covers the second electrodecarrier layer.

Embodiment 21

The test element according to any one of the preceding embodiments,wherein the test element is a test strip.

Embodiment 22

The test element according to any one of the preceding embodiments,wherein the capillary is open at three sides.

Embodiment 23

The test element according to any one of the preceding embodiments,wherein a sample of bodily fluid is applicable to one or more of: a sidedose position, a top dose position, a front dose position.

Embodiment 24

The test element according to any one of the preceding embodiments,wherein the test element comprises a top dose position and furthercomprises a through hole extending through a cover foil into thecapillary, in particular extending through a cover foil into thecapillary in a way that the condition that the increment of a wettedsurface area dA1 of the first electrode per increment dV of a filledvolume of the capillary at all times equals an increment of a wettedsurface area dA2 of the second electrode is still met.

Embodiment 25

The test element according to any one of the preceding embodiments,wherein the test element has an elongated shape extending along alongitudinal axis, wherein the capillary at least partially extendsalong the longitudinal axis of the test element.

Embodiment 26

The test element according to any one of the preceding embodiments,wherein the test element has an elongated shape extending along alongitudinal axis, wherein the capillary at least partially extendsperpendicular to the longitudinal axis.

Embodiment 27

The test element according to the preceding embodiment, wherein thecapillary extends from a first opening at a first longitudinal edge ofthe test element to a second opening at a second longitudinal edge ofthe test element.

Embodiment 28

The test element according to the preceding embodiment, wherein the testelement comprises a side dose position located at one or both of thefirst opening or the second opening.

Embodiment 29

The test element according to any one of the three precedingembodiments, wherein the capillary has an open side at a front face ofthe test element.

Embodiment 30

The test element according to the preceding embodiment, wherein the testelement has a front dose position located at the front face of the testelement.

Embodiment 31

The test element according to any one of the preceding embodiments,wherein the capillary comprises a vent hole opening.

Embodiment 32

The test element according to any one of the preceding embodiments,wherein the test element comprises a strip handle.

Embodiment 33

The test element according to the preceding embodiment, wherein the testelement comprises a layer setup disposed on top of at least one carrierelement, wherein the carrier element, in a longitudinal direction of thetest element, protrudes from the layer setup, thereby forming the striphandle.

Embodiment 34

The test element according to any one of the preceding embodiments,wherein the test element comprises a first electrode contact zone and asecond electrode contact zone configured to contact the first electrodeand the second electrode with a further device, in particular a meter.

Embodiment 35

The test element according to the preceding embodiment, wherein thefirst electrode contact zone and the second electrode contact zone areconfigured to be electrically contacted from the same side of the testelement.

Embodiment 36

The test element according to the preceding embodiment, wherein thefirst electrode contact zone and the second electrode contact zone arearranged in different layers of a layer setup of the test element,wherein one of the first electrode contact zone and the second electrodecontact zone protrudes over the other one of the first electrode contactzone and the second electrode contact zone.

Embodiment 37

The test element according to the preceding embodiment, wherein thefirst electrode contact zone and the second electrode contact zone formdifferent steps of a staircase configuration of the layer setup.

Embodiment 38

The test element according to any one of the four preceding embodiments,wherein the first electrode contact zone and the second electrodecontact zone are configured to be electrically contacted from opposingsides of the test element.

Embodiment 39

The test element according to the preceding embodiment, wherein apunched hole through a cover foil and a spacer layer is configured asthe second electrode contact zone, in particular a contact hole.

Embodiment 40

The test element according to any one of the preceding embodiments,wherein the test element comprises at least one carrier element.

Embodiment 41

The test element according to any one of the preceding embodiments,wherein the test element comprises a layer setup, wherein the firstelectrode comprises at least one first electrode conductive layerdisposed on at least one first electrode carrier layer, wherein thesecond electrode comprises at least one second electrode conductivelayer disposed on at least one second electrode carrier layer.

Embodiment 42

The test element according to the preceding embodiment, wherein thelayer setup is arranged such that the first electrode conductive layerfaces the second electrode conductive layer, with the capillary inbetween.

Embodiment 43

The test element according to any one of the two preceding embodiments,wherein at least one spacer layer is disposed in between the firstelectrode conductive layer and the second electrode conductive layer.

Embodiment 44

The test element according to any one of the preceding embodiments,wherein one or both of the first electrode or the second electrode areelectrically contacted by at least one electrically conductive turnoverelement, wherein the first or second electrode, respectively, areoriented to face a first direction, wherein the electrically conductiveturnover element is contactable from a second direction, the seconddirection being an opposite direction of the first direction.

Embodiment 45

The test element according to the preceding embodiment, wherein theelectrically conductive turnover element comprises at least one of anelectrically conductive layer or an electrically conductive foil havinga first section and a second section, the first section electricallycontacting the first or second electrode, respectively, and the secondsection being electrically contactable.

Embodiment 46

The test element according to the preceding embodiment, wherein theelectrically conductive turnover element is partially covered by atleast one layer comprising the first or second electrode, respectively,wherein the second section is located in an uncovered region.

Embodiment 47

The test element according to any one of the two preceding embodiments,wherein the electrically conductive turnover element is laminated to thefirst or second electrode, respectively.

Embodiment 48

A method for producing a test element according to any one of thepreceding embodiments, the method comprising at least one step offorming a layer setup, wherein the first electrode, the second electrodeand the capillary are formed such that the first electrode and thesecond electrode are arranged on opposing sides of the capillary.

Embodiment 49

The method according to the preceding embodiment, wherein the testelement is a test strip.

Embodiment 50

The method according to any one of the preceding method embodiments,wherein the test element is produced in a continuous process, typicallyin a reel-to-reel process.

Embodiment 51

The method according to any one of the preceding method embodiments,wherein the step of forming the layer setup comprises at least onelamination step, wherein, in the lamination step, at least two layersare combined by a lamination process.

Embodiment 52

The method according to the preceding embodiment, wherein the laminationstep comprises a lamination of at least two tapes.

Embodiment 53

The method according to any one of the preceding method embodiments, themethod further comprises cutting the layer setup into test strips.

Embodiment 54

The method according to the preceding embodiment, wherein the layersetup is a tape-shaped layer setup, wherein a width of the tape-shapedlayer setup defines a length of the test strips.

Embodiment 55

The method according any one of the preceding method embodiments,wherein the forming of the capillary comprises cutting out the capillaryfrom at least one spacer layer.

Embodiment 56

The method according to the preceding embodiment, wherein the cuttingcomprises a kiss-cut process.

Embodiment 57

The method according to any one of the five preceding embodiments,wherein the working electrode comprises at least one reagent, whereinthe method comprises coating a reagent stripe onto at least one carrierlayer.

Embodiment 58

The method according to the preceding embodiment, wherein the coatingcomprises a die coating process.

Embodiment 59

The method according to the preceding embodiment, wherein the diecoating further comprises running the reagent stripe through a drierfollowing a coating device.

Embodiment 60

A system for determining at least one property of a sample, the systemcomprising at least one test element according to any one of thepreceding embodiments referring to a test element, the system furthercomprising at least one measurement device adapted for performing atleast one electrical measurement using the test element.

Embodiment 61

The system according to the preceding embodiment, wherein the testelement comprises at least one first electrode and at least one secondelectrode, wherein the first electrode is designed as a workingelectrode and the second electrode is designed as a counter electrode,wherein the test element comprises at least one capillary capable ofreceiving a sample of the body fluid, wherein the first electrode andthe second electrode are arranged on opposing sides of the capillary,wherein the first electrode and the second electrode and the capillaryin between the first electrode and the second electrode form anelectrochemical cell, wherein the test element is configured to detectthe at least one analyte independently of a filling level of theelectrochemical cell, wherein the first electrode and the secondelectrode are arranged such that during a capillary filling the firstelectrode and the second electrode are wetted simultaneously and at anequal rate, the system further comprising at least one measurementdevice adapted for performing at least one electrical measurement usingthe test element, wherein the measurement device is configured to detectboth an AC signal and a DC signal, wherein the measurement device isconfigured to detect the at least one analyte independently of a fillinglevel of the electrochemical cell.

Embodiment 62

The system according to any one of the preceding embodiments referringto a system, wherein the measurement device is configured to perform atleast one impedance measurement using the first electrode and the secondelectrode.

Embodiment 63

The system according to any one of the two preceding embodiments,wherein the measurement device further is configured to perform at leastone amperometric measurement using the first electrode and the secondelectrode.

Embodiment 64

The system according to any one of the preceding embodiments referringto a system, wherein the measurement device is configured to detect bothan AC signal and a DC signal.

Embodiment 65

The system according to the preceding embodiment, wherein themeasurement device is configured to detect the AC signal and the DCsignal sequentially.

Embodiment 66

The system according to any one of the two preceding embodiments,wherein the measurement device is configured to apply an AC signal tothe first electrode and the second electrode and to detect a response.

Embodiment 67

The system according to any one of the preceding embodiments referringto a system, wherein the measurement device is further configured toelectrically monitor a filling process of the capillary.

Embodiment 68

The system according to any one of the preceding embodiments referringto a system, wherein the measurement device is configured to perform atleast one initial failsafe measurement before applying the sample ofbodily fluid.

Embodiment 69

The system according to the preceding embodiment, wherein the failsafemeasurement comprises at least one electrical measurement using thefirst electrode and the second electrode.

Embodiment 70

The system according to the preceding embodiment, wherein the electricalmeasurement is used for deriving at least one electrical measurementvalue, wherein the failsafe measurement further comprises comparing theelectrical measurement value with at least one threshold value.

Embodiment 71

The system according to any one of the three preceding embodiments,wherein the failsafe measurement comprises detecting at least one damageand/or deterioration of at least one of the first electrode or thesecond electrode.

Embodiment 72

A method for determining at least one property of a sample, wherein asystem according to any one of the preceding embodiments referring to asystem is used, wherein the method comprises the following steps:

a) Connecting the test element to at least one measurement device;b) Applying a sample of bodily fluid to a capillary of at least one testelement;c) Determining both an AC signal and a DC signal;d) Calibrating measurement results by using the AC and DC signal.

Embodiment 73

The method according to the preceding embodiment, wherein the AC signaland the DC signal are determined simultaneously or sequentially.

Embodiment 74

The method according to any one of the preceding embodiments referringto a method for determining at least one property of a sample, whereinthe determination of the AC and DC signal is performed by overlappingexcitation potentials.

Embodiment 75

The method according to any one of the preceding embodiments referringto a method for determining at least one property of a sample, whereinboth the AC signal and the DC signal are proportional to the fillinglevel of the capillary such that effects due to a filling of thecapillary are compensated.

Embodiment 76

The method according to any one of the preceding embodiments referringto a method for determining at least one property of a sample, whereinthe method further comprises determining a contact time, wherein an ACsignal is applied between at least one first electrode and at least onesecond electrode of the test element, wherein a response over time ismeasured, wherein the response is compared to a predefined threshold.

Embodiment 77

The method according to any one of the preceding embodiments referringto a method for determining at least one property of a sample, whereinthe method further comprises determining a filling level of thecapillary, wherein an AC signal is applied between the at least onefirst electrode and the at least one second electrode of the testelement, wherein a response signal over time is measured, wherein theresponse is compared to at least one predefined threshold, wherein thepredetermined threshold is chosen such that a minimum filling level isensured.

Embodiment 78

The method according to the preceding embodiment, wherein the predefinedthreshold is chosen with respect to a specific conductivity of a sample.

Embodiment 79

The method according to any one of the preceding embodiments referringto a method for determining at least one property of a sample, whereinthe method further comprises monitoring a filling process of thecapillary, wherein a DC voltage is applied between the first electrodeand the second electrode, wherein a DC response is detected, wherein theDC response is compared to a predefined limit.

In FIGS. 1 to 3 a first embodiment of a test element 110 according tothe present disclosure is shown. FIG. 1 shows an exemplary arrangementof different layers of a tape-shaped layer setup of the test element110, in particular before cutting the layer setup into individual testelements 110, whereas in FIG. 2 an exploded drawing of one individualtest element 110 is depicted. The test element 110 is adapted forelectrochemically detecting at least one analyte in a bodily fluid. Theat least one analyte may be a component or compound present in a bodyfluid and the concentration of which may be of interest for a user. Asan example, the at least one analyte may be selected from the groupconsisting of glucose, cholesterol, triglycerides, and lactate.Additionally or alternatively, however, other types of analytes may beused and/or any combination of analytes may be determined. The bodyfluid may be whole blood, such as a sample of capillary blood taken froma finger stick.

The test element 110 may comprise at least one carrier element 112, suchas at least one carrier foil. For example, the carrier element 112 maybe a polymer foil that may be configured to provide stability for thetest element 110, such that it can be handled by a user, typicallywithout deflections and/or fractions. An adhesive layer 114 may belaminated onto the carrier element 112.

The test element 110 comprises at least one first electrode 116 and atleast one second electrode 118. The first electrode 116 is designed as aworking electrode and the second electrode 118 is designed as a counterelectrode. The first electrode 116 and the second electrode 118 may bemade of a non-corrosive and non-passivating material. In the firstembodiment shown in FIGS. 1 to 3, the first electrode 116 may bearranged on top of the adhesive layer 114. The first electrode 116 maycomprise at least one first electrode conductive layer 120. The firstelectrode conductive layer 120 may comprise at least one of: a metallayer, typically a noble metal layer selected from the group consistingof palladium, platinum, silver and gold; a conductive carbon layer, inparticular a carbon paste layer. The first electrode conductive layer120 may be disposed on a first electrode carrier layer 122, such as afirst electrode carrier foil. For example, the first electrode carrierlayer 122 may be coated with a conductive carbon paste or with a noblemetal layer, e.g., gold, palladium or platinum. The first electrodeconductive layer 120 may extend from a first longitudinal edge 124 ofthe first electrode carrier layer 122 to a second longitudinal edge 126of the first electrode carrier layer 122. The first electrode conductivelayer 120 may fully cover the first electrode carrier layer 122. Thefirst electrode 116 may comprise at least one reagent coating 128 incontact with the first electrode conductive layer 120. The reagentcoating 128 may comprise at least one reagent stripe coated onto thefirst electrode conductive layer 120. For example, the reagent stripemay be coated by a die coating process by a coating device and may bedried by running through a drier following the coating device.

The test element 110 may comprise a strip handle 132. The test element110 shown may comprise a layer setup disposed on top of the carrierelement 112. The carrier element 112, along a longitudinal axis 130 ofthe test element 110, may protrude from the layer setup, thereby formingthe strip handle 132. Therefore, the first electrode carrier layer 122may have a smaller width than the width of the carrier element 112.Additionally or alternatively, embodiments are feasible, wherein thetest element 110 may be configured without a protruding carrier element112 as strip handle 132. In this embodiment, a length of the testelement 110 may be such that a user may grip between a dosing side and afurther device in which the test element 110 may be inserted.

On top of the first electrode 116, a spacer layer 134, such as a polymerfoil, may be laminated. In between the first electrode 116 and thespacer layer 134, an adhesive layer 136 may be positioned. The testelement 110 may comprise a first electrode contact zone 138 configuredto contact the first electrode 116 with a further device. The spacerlayer 134 may have a smaller width than the width of the first electrodecarrier layer 122. The spacer layer 134 may be arranged such that partsof the first electrode carrier layer 122 may be uncovered by the spacerlayer 134, in particular such that the first electrode carrier layer 122may protrude from the spacer layer 134 on both sides. Thus, on oneprotruding side the first electrode contact zone 138 may be created andon the other side a measurement zone 140 may be created. The spacerlayer 134 may be coated with a conductive material layer 142, e.g., thespacer layer 134 may be sputtered with a thin silver layer. Further, ontop of the conductive material layer 142 a conductive adhesive layer144, such as a silver particle based adhesive layer, may be laminated.The test element 110 may comprise a second electrode contact zone 146configured to contact the second electrode 118 with the further device.The conductive adhesive layer 144 may have a smaller width that thewidth of the spacer layer 134. The conductive adhesive layer 144 may bepositioned such that a part of the conductive material layer 144pointing to the first electrode contact zone 138 may be uncovered by theconductive adhesive layer 144, in particular such that the conductivematerial layer 144 may protrude from the conductive adhesive 144 on oneside. Thus, the second electrode contact zone 146 may be created.

The second electrode 118 may be arranged on top of the conductiveadhesive layer 144. The first electrode 116 and the second electrode 118may have the same dimension. The second electrode 118 may comprise atleast one second electrode conductive layer 148. The second electrodeconductive layer 148 may comprise at least one of: a metal layer,typically a noble metal layer selected from the group consisting ofpalladium, platinum, silver or gold; a conductive carbon layer, inparticular a carbon paste layer. The second electrode conductive layer148 may be disposed on a second electrode carrier layer 150, such as asecond electrode carrier foil. For example, the second electrode carrierlayer 150 may be metallized on one side facing after a lamination stepthe spacer layer 134, typically by a silver layer. For example, thesecond electrode carrier layer 150 may be coated by a conductiveadhesive layer 151, e.g., based on silver particles. The secondelectrode 118 may further comprise Ag/AgCl, in particular an Ag/AgClpaste. For example, in this first embodiment, the metallized side of theelectrode carrier layer 150 may be coated with a strip of an Ag/AgClpaste 152. The second electrode conductive layer 148 may extend from afirst longitudinal edge 154 of the second electrode carrier layer 150 toa second longitudinal edge 156 of the second electrode carrier layer150. The second electrode conductive layer 148 may fully cover thesecond electrode carrier layer 150. The strip of Ag/AgCl paste may bepositioned such that after the lamination step, the second electrodecarrier layer 150 may face the reagent coating 128. In an alternativeembodiment, instead of the silver layer coating, the electrode carrierlayer 150 may be coated completely by an Ag/AgCl paste. In a furtheralternative embodiment, a redox electrode can be used as the counterelectrode. Such a redox electrode comprises a conductive layer, e.g., aconductive carbon layer, coated with a reagent layer comprising anreducible substance, e.g., an organic redox mediator. Arrows 158 shownin FIG. 1 indicate that the depicted laminated second electrode 118 maybe turned onto the conductive adhesive 144.

The test element 110 comprises at least one capillary 160 capable ofreceiving a sample of the body fluid. The first electrode 116 and thesecond electrode 118 are arranged on opposing sides of the capillary160. The first electrode 116 and the second electrode 118 may bearranged as opposing electrodes, such that a surface of the firstelectrode 116 faces a surface of the second electrode 118. The firstelectrode 116 and the second electrode 118 may be aligned in parallel.The first electrode 116 and the second electrode 118 and the capillary160 in between the first electrode 116 and the second electrode 118 mayform an electrochemical cell. By laminating the second electrode 118onto the conductive adhesive 144, the electrochemical cell may becreated. The electrochemical cell may extend over the full length of thecapillary 160. A height of the electrochemical cell may be defined by athickness of the spacer layer 134 and adhesive layers in between thefirst electrode 116 and the second electrode 118. To avoid a change ofthe height of the electrochemical cell during a measurement, e.g., whenthe strip handle 132 is touched by a user such that the test element 110is bent, the adhesive layer 114 may be designed such that a regiondefined by a position of the electrochemical cell may be not covered bythe adhesive layer 114 such that a gap 161 between the carrier element112 and the first electrode 116 may be formed, see FIG. 3B. Thus, incase a user may inadvertently bend the test element 110, a distancebetween the first and the second electrode surfaces may be unaffected.The first electrode 116 may extend over a full length of the capillary160. The second electrode 118 may extend over a full length of thecapillary 160. The first electrode 116 and the second electrode 118 arearranged such that during a capillary filling the first electrode 116and the second electrode 118 are wetted simultaneously and at an equalrate. An increment of a wetted surface area dA1 of the first electrode116 per increment dV of a filled volume of the capillary 160 at alltimes may equal an increment of a wetted surface area dA2 of the secondelectrode 118. Thus, the test element 110 may be configured to detectthe at least one analyte independently of a filling level of theelectrochemical cell.

The test element 110 may be produced in a method according to thepresent disclosure. The method comprises at least one step of forming alayer setup, e.g., as the layer setup shown in FIGS. 1 to 3. The testelement 110 may be produced in a continuous process, typically in areel-to-reel process. The step of forming the layer setup may compriseat least one lamination step, wherein, in the lamination step, at leasttwo layers are combined by a lamination process. The lamination step maycomprise a lamination of at least two tapes. The method further maycomprise cutting the layer setup into individual test elements 110 suchas test strips. The cutting and cutting lines 162 are indicated inFIG. 1. The layer setup may be a tape-shaped layer setup, wherein awidth of the tape-shaped layer setup may define a length of the teststrip. The resulting test element 110 may have an elongated shapeextending along the longitudinal axis 130, wherein the capillary 160 mayat least partially extend perpendicular to the longitudinal axis 130 ofthe test element 110. By cutting the layer setup into individual testelements 110, the capillary 160 may be open at three sides. According tothe present disclosure, the sample of body fluid may be applicable toone or more of: a side dose position, a top dose position, a front doseposition. In the first embodiment of the test element 110, the capillary160 may have two side dose positions 164 and one front dose position166, best seen in FIG. 3A. The capillary 160 may extend from a firstopening at a first longitudinal edge of the test element 110, e.g., afirst side dose position 164, to a second opening at a secondlongitudinal edge of the test element 110, e.g., a second side doseposition 164. The side dose positions may be an ideal applicationposition for capillary blood from a finger stick. The test element 110may have an open side at a front face 168 of the test element 110. Thetest element 110 may have one front dose position 166 located at thefront face 168 of the test element 110. In front of the capillary 160,such as in direction of the strip handle 132, the carrier element 112may be coated with a hydrophobic coating. FIG. 3B shows a cross-sectionof the test element 110.

As outlined above, the test element 110 may comprise the first electrodecontact zone 138 and the second electrode contact zone 146 configured tocontact the first electrode 116 and the second electrode 118 with afurther device. In FIG. 3A, a system according to the present disclosureis shown. The system 170 comprises at least one test element 110. Thesystem further comprises at least one measurement device 172 adapted forperforming at least one electrical measurement using the test element110. The first electrode contact zone 138 and the second electrodecontact zone 146 may be configured to be electrically contacted from thesame side 174 of the test element 110. The first electrode contact zone138 and the second electrode contact zone 146 may be arranged indifferent layers of a layer setup of the test element 110, wherein oneof the first electrode contact zone 138 and the second electrode contactzone 146 may protrude over the other one of the first electrode contactzone 138 and the second electrode contact zone 146. The first electrodecontact zone 138 and the second electrode contact zone 146 may formdifferent steps of a staircase configuration of the layer setup.However, as the first electrode 116 and the second electrode 118 may beconfigured as opposing electrodes, to allow an electrically contact fromthe same side 174 of the test element 110, the first electrode 116 orthe second electrode 118 may be electrically contacted by at least oneelectrically conductive turnover element 176. The first electrode 116 orthe second electrode 118, respectively, may be oriented to face a firstdirection, wherein the electrically conductive turnover element 176 maybe contactable from a second direction, the second direction being anopposite direction of the first direction. The electrically conductiveturnover element 176 may comprise at least one of an electricallyconductive layer or an electrically conductive foil having a firstsection and a second section, the first section electrically contactingthe first electrode 116 or the second electrode 118, respectively, andthe second section being electrically contactable. The electricallyconductive turnover element 176 may be partially covered by at least onelayer comprising the first electrode 116 or the second electrode 118,respectively, wherein the second section may be located in an uncoveredregion. The electrically conductive turnover element 176 may belaminated to the first electrode 116 or second electrode 118,respectively. For example, the conductive material layer 142 and theconductive adhesive layer 144 may be adapted as turnover element 176.The first electrode contact zone 138 and second electrode contact zone146 may be hit upon by at least one connector 178 of the measurementdevice 172, e.g., meter connector pins. The measurement device 172 mayhave two pairs of connectors 178, one pair for each of the firstelectrode 116 and the second electrode 118. One connector 178 of eachconnector pair may be configured to support a current flow through thetest element 110. The other connector 178 may be used to detect avoltage. Such a configuration, also called 4-wire-technique, may allowan electronic controller of the measurement device 172 to compensatevoltage drop induced by parasitic transfer resistances at connectionspots of the first electrode contact zones 138 and second electrodecontact zones 146 and the connectors 178.

The measurement device 172 may be configured to perform at least oneimpedance measurement using the first electrode 116 and the secondelectrode 118. The measurement device 172 may be configured to apply anAC signal to the first electrode 116 and the second electrode 118 and todetect a response. The measurement device 172 may be configured toperform at least one initial failsafe measurement before applying thesample of bodily fluid. The failsafe measurement may comprise at leastone electrical measurement using the first electrode 116 and the secondelectrode 118. The electrical measurement may be used for deriving atleast one electrical measurement value, wherein the failsafe measurementfurther may comprise comparing the electrical measurement value with atleast one threshold value. The failsafe measurement may comprisedetecting at least one damage and/or deterioration of at least one ofthe first electrode 116 or the second electrode 118. The at least onedamage and/or deterioration, such as a scratch on a conductive surfaceof the first electrode 116 and/or the second electrode 118, may resultin interrupting the conductive surface before or within theelectrochemical cell.

FIG. 4A shows a histogram of an impedance measurement of a failsafemeasurement. For this measurement, an AC signal may be applied to thefirst electrode 116 and the second electrode 118, in particular a 10 mVrms (root mean square) AC voltage, and the complex impedance may bemeasured. The histogram shows the resulting admittance Y at differentfrequencies f measured between the first electrode 116 and the secondelectrode 118. Measurement results of five test elements 110 withscratches applied to on one of the first electrode conductive layer 120close to the first electrode contact zone 138 or the second electrodeconductive layer 148 close to the second electrode contact zone 146,indicated as crosses, are compared to measurement results of five testelements 110 with scratches applied to on one of the first electrodeconductive layer 120 close to the electrochemical cell or the secondelectrode conductive layer 148 close to the electrochemical cell,indicated as triangles, and to measurement results of test elements 110with no scratches, indicated as rhombus. The measurement results show ashift of the admittance. Thus, by using a phase information and anadmittance information at different frequencies, it may be possible toseparate the effect of scratches from otherwise changed conductivities,for example caused by a variable thickness of the first electrode and/orsecond electrode conductive layers 120, 148.

The measurement device 172 may further be configured to perform at leastone amperometric measurement using the first electrode 116 and thesecond electrode 118. The measurement device 172 may be configured todetect both an AC signal and a DC signal. The measurement device 172 maybe configured to detect the AC signal and the DC signal sequentially.The measurement device 172 may be further configured to electricallymonitor a filling process of the capillary 160. An AC signal may beapplied to the first electrode 116 and the second electrode 118. Afterit was detected that the sample of body fluid touches first the firstelectrode 116 and the second electrode 118, the AC response may furtherincrease, because the wetted surface area dA1 of the first electrode 116and the wetted surface area dA2 of the second electrode 118 may increasecontinuously. If the response signal may reach a certain threshold, thistime may be detected as “Filling complete” and a test sequence to carryout an analytical measurement of the at least one analyte in the bodyfluid may start. The term to reach a constant value may refer to aresponse gradient falls under a predefined threshold. In case themeasurement device 172 may not detect the response signal reaching aconstant value within a predefined time, an error message may begenerated by the measurement device 172 and/or the measurement may bestopped. FIG. 4B shows a histogram used for monitoring a filling processfor three different blood samples, adjusted to different hematocritlevels of 70% (long dashed set of curves), 43% (short dashed set ofcurves), and 0% (dotted set of curves). The AC signal was integrated andis depicted as admittance Y versus a filling time t after detecting thatthe sample of body fluid touches first the first electrode 116 and thesecond electrode 118. The vertical dashed arrows 180 indicate the timewhere the constant value is reached. The horizontal arrow 182 indicatesa period of time to reach the constant value.

A second embodiment of the test element 110 is shown in FIGS. 5A to 7.For a detailed description of the layer setup of the test element 110,reference can be made to the description of the first embodiment aboveor a description of further embodiments given below. In the secondembodiment of the test element 110, the capillary 160 may have two sidedose positions 164 and one top dose position 184, see, e.g., FIGS. 5Aand 5B. The capillary 160 may extend from a first opening at a firstlongitudinal edge of the test element 110, e.g., the first side doseposition 164, to a second opening at a second longitudinal edge of thetest element 110, e.g., the second side dose position 164. The side dosepositions may be an ideal application position for capillary blood froma finger stick. The test element 110 may comprise the top dose position184 and further may comprise a through hole extending through a coverfoil, e.g., the first electrode carrier layer 122, into the capillary160. The top dose position 184 may be an ideal application position fordosing the sample with a transfer device, e.g., a pipette.

The first electrode contact zone 138 and the second electrode contactzone 146 may be configured to be electrically contacted from opposingsides of the test element 110. The first electrode contact zone 138 mayprotrude of the layer setup of the test element 110. A punched holethrough the cover foil and the spacer layer 134 may be configured as thesecond electrode contact zone 146, in particular a contact hole 186. Ina particular embodiment, two contact holes are punched through the coverfoil and the spacer layer 134. Alternatively in a continuous productionprocess, one contact hole is punched at the position where the testelements are individualized in a subsequent cutting process (cuttingline) resulting in test elements comprising two lateral contact zones onopposing edges of the final test element. Embodiments with two contactholes or contact zones for each electrode are advantageous if4-wire-technique is used. The contact hole 186 may have a rectangularshape. FIGS. 5A and 5B show the second electrode being contacted by theconnector 178, such as a pair of connectors 178, through the contacthole 186. Thus, the measurement device 172 may comprise one pair ofconnectors 178 configured to contact the first electrode 116, in thisembodiment shown in FIGS. 5A and 5B, from a first direction by the firstelectrode contact zone 138 and to contact the second electrode 118 froma second direction on the opposite side of the test element 110 throughthe contact hole 186.

The contact hole 186 and the top dose position 184 may be realized bypunched holes through the cover foil and the spacer layer 134, before alamination step of the test element 110, typically in one punching step.These holes, the contact hole 186 and the top dose position 184, may beused to trigger a cutting such that the width of an individual testelement 110 may be defined by a distance of the punched holes along thecover foil and such that the holes may be positioned in a middle of thewidth of each test element 110. For this embodiment, no additionalturnover element 176 may be required. FIG. 6 shows an exploded drawingof the second embodiment of the test element 110. Regarding the design,structure and production of the first electrode 116 and the secondelectrode 118, reference can be made to the description of the firstembodiment of the test element 110. The spacer layer 134 may be designedcomprising at least two portions. The term “in at least two portions”refers to that embodiments, wherein the spacer layer 134 may be designedcomprising more than two portions may be feasible, too. Onto the firstelectrode 116 a first portion 188 of the spacer layer 134 covered withan adhesive layer 189, 191 on both sides may be laminated, such that achannel may be created at the position of the reagent coating 128. Awidth of the first portion 188 of the spacer layer 134 may be configuredsuch that the first electrode 116 may be partially uncovered, formingthe first electrode contact zone 138. Further, onto the first electrode116 a second portion 190 may be laminated, such that a width andposition of the channel between the spacer layer 134 and the firstelectrode 116 is defined, wherein a width of the second portion 190 maybe smaller than a width of the first portion 188. The right column ofFIG. 7 shows a laminated layer setup of the first electrode 116 andspacer layer 134.

Further, in a punching step, the holes, the contact hole 186 and the topdose position 184, may be punched through the laminated layer setup ofthe first electrode 116 and spacer layer 134 by a punching device,typically within one punching step. The punching step may be performedin a continuous process such as a reel-to-reel process. The spacer layer134 may be covered by a release liner. The top dose position 184 may bearranged such that the punched hole may touch the capillary 160 at oneedge. The contact hole 186 may be arranged at an opposing edge of thetest element 110. After the punching step, the release liner may beremoved from the spacer layer 134. The middle column of FIG. 7 shows thelaminated layer setup of the first electrode 116 and spacer layer 134after the punching step. In a further lamination step, the laminatedlayer setup of the first electrode 116 and spacer layer 134 may beturned onto the second electrode 118 and may be laminated with thesecond electrode 118. Arrows 158 shown in FIG. 7 indicate that thedepicted laminated second electrode 118 may be turned onto theconductive adhesive 144. The second electrode carrier layer 150 may beconfigured as the cover foil of the test element 110. The secondelectrode carrier layer 150 may be coated on one side with the secondelectrode conductive layer 148, e.g., the second electrode carrier layer150 may be sputtered with a silver layer. At the position of thecapillary 160 an Ag/AgCl paste stripe may be arranged. The laminatedsecond electrode is depicted in the left column of FIG. 7. Finally, thelayer setup may be cut into individual test elements 110 such as teststrips. The cutting and cutting lines 162 are indicated in FIG. 7.

A third embodiment of the test element 110 is shown in FIGS. 8A to 10.For a detailed description of the layer setup of the test element 110,reference can be made to the description of the first and secondembodiment above or a description of further embodiments given below. Asin the second embodiment, the first electrode 116 and the secondelectrode 118 may be contacted from opposing sides of the test element110, e.g., by connectors 178 of the measurement device 172. In the thirdembodiment of the test element 110, the capillary 160 may at leastpartially extend along the longitudinal axis 130 of the test element110, depicted e.g., in FIG. 8B. The forming of the capillary 160 maycomprise cutting out the capillary 160 from the spacer layer 134. Thus,the spacer layer 134 may be covered on both sides by an adhesivelaminated by a release liner. The cutting may comprise a kiss-cutprocess. In the cutting process, a cutting profile wheel may be used.The spacer layer 134 may run through a gap between two contrary rotatingwheels, wherein one of the wheels may be a kiss-cut wheel with arepeated outlined shape of the capillary 160 at a perimeter. By runningthrough the rotating wheels, the outlined capillary shape may be cutinto the spacer layer 134 down to a surface of the opposing releaseliner. FIG. 8B shows the capillary 160 cut out of the spacer layer 134laminated on the second electrode 118, whereas FIG. 8C shows a crosssection of the test element 110.

The first electrode carrier layer 122 may be coated with a carbon pasteor sputtered with a noble metal layer. The reagent coating 128, e.g.,the reagent strip, may be arranged close to the measurement device 172,in particular close to a heating device of the measurement device. Thus,it may be possible to heat the sample of body fluid above an ambienttemperature, allowing coagulation status parameters to be tested inwhole blood samples. The position of the reagent coating 128 may definethe measurement zone of the test element 110. The test element 110 mayfurther comprise a vent hole opening 192. Adjacent to the reagentcoating, in the direction of the first electrode contact zone 138, thefirst electrode 116 may be coated by a second reagent, such that ahydrophobic surface 194 following the measurement zone may be created.Hence, the sample of body fluid may be hindered to pass an end of thecapillary 160 up to the vent hole 192, such that the measurement device172 may be contaminated. However, other parts of the surface of thefirst electrode 116 may be hydrophilic, such that a quick sampletransport is ensured. Therefore, the surface may be treated with adetergent. FIG. 9 shows an exploded drawing of the test element 110.

After the kiss-cut process, one of the release liners may be removedfrom the spacer layer 134 and the spacer layer 134 may be laminated tothe first electrode 116. The spacer layer 134 may be covered withadhesive layers 189, 191 on both sides. Then cut out inner parts 196 ofthe capillary structure may be pulled off such that outer parts 198 ofthe capillary structure remain on the first electrode 116. This removingstep is depicted on the right column of FIG. 10, e.g., the pulling offis indicated by arrow 200. The structure of the capillary may be used toalign the vent hole 192, the top dose position 184, and the secondcontact hole 186. In a further lamination step, the laminated layersetup of the first electrode 116 and spacer layer 134, shown in themiddle column of FIG. 10, may be turned onto the second electrode 118and may be laminated with the second electrode 118, indicated by arrow158 shown in FIG. 10. The laminated second electrode is depicted in theleft column of FIG. 7. Finally, the layer setup may be cut intoindividual test elements 110 such as test strips. The cutting andcutting lines 162 are indicated in FIG. 10.

FIG. 11 shows an exploded drawing of an embodiment of the test element110. In this embodiment, the first electrode carrier layer 122 may becovered by a sputtered aluminum layer 202. The usage of an aluminumlayer may be advantageous because of lower raw material costs and betterelectrical conductivity than carbon pastes or inks. However, thealuminum layer cannot be used directly as electrode material forsupporting a redox reaction, because of an oxide layer on a surface ofthe aluminum layer. The aluminum layer 202 may be combined with aconductive carbon paste. Thus, onto the aluminum layer 202 at a positionof the electrochemical cell, a stripe of carbon 204 may be coated. Thereagent coating 128 may be coated on top of the carbon stripe 204. Anadhesive layer 205 may be arranged between the carbon stripe 204 and thespacer layer 134. The turnover element 176 may be arranged on top of thespacer layer 134, e.g., the turnover element 176 may be designed as aconductive adhesive and a conductive carbon coating. Another side of thespacer layer 134 may be coated with an adhesive layer 206.Alternatively, active ingredients of the detection reagent of thereagent coating 128 may be mixed with the carbon paste and may be coateddirectly on the aluminum surface. In another embodiment, a conductivecarbon transfer adhesive foil may be used, which may be coatedhomogenously with the reagent coating 128 and may be laminated onto thealuminum layer 202. The usage of carbon on aluminum may be feasible forall described embodiments. In embodiments, wherein the test element 110may be configured without a protruding carrier element 112 as striphandle 132, a usage of carbon on aluminum may be feasible, too. In theseembodiments, the carrier element 112 may be coated with aluminum with acoated carbon stripe and a reagent coating at the position of theelectrochemical cell.

FIG. 12 shows an exploded drawing of an embodiment of the test element110 according to the present disclosure. FIGS. 13A and 13B show a topview and a bottom view of this embodiment. The test element 110 maycomprise a layer setup. The first electrode 116, which is designed asworking electrode, may comprise at least one first electrode conductivelayer 120. The first electrode conductive layer 120 may comprise acarbon ink coating. The first electrode conductive layer 120 may bedisposed on at least one first electrode carrier layer 122. The firstelectrode carrier layer 122 may be a foil, e.g., a top foil. The firstelectrode 116 may comprise at least one reagent coating 128, e.g., adetection reagent coating, in contact with the first electrodeconductive layer 120. The reagent coating 128 may cover at leastpartially the first electrode conductive layer 120. The reagent layer128 may extend over the whole width and length of the capillary 160.

The second electrode 118, which may be designed as counter electrode,may comprise at least one second electrode conductive layer 148. Thesecond electrode conductive layer 148 may comprise a carbon ink coating.The second electrode conductive layer 148 may be disposed on at leastone second electrode carrier layer 150. The second electrode carrierlayer 150 may be a foil, e.g., a bottom foil. The counter electrode maycomprise at least one reagent coating 128 in contact with the secondelectrode conductive layer 148. The reagent coating 128 may comprise aredox chemistry. The reagent coating may comprise an Ag/AgCl ink. Thereagent coating 128 may cover at least partially the second electrodeconductive layer 148. The reagent layer 128 may extend over the wholewidth and length of the capillary 160. The reagent coatings of the firstelectrode 116 and the second electrode 118 may cover equal areas of therespective electrode conductive layers 120, 148.

At least one spacer layer 134 may be disposed in between the firstelectrode conductive layer 120 and the second electrode conductive layer148. The first electrode 116 and the second electrode 118 and thecapillary 160 in between the first electrode 116 and the secondelectrode 118 form an electrochemical cell. The electrochemical cell mayextend over the full length of the capillary 160. The first electrode116 and the second electrode 118 may extend over the full length of thecapillary 160. The spacer layer 134 may be arranged such that it doesnot extend over the full length of the test element 110. For example,the spacer layer 134 may cover the capillary 160 partly. The capillary160 may be open at three sides. The sample of bodily fluid may beapplicable to a side dose position 164 and a front dose position 166,which can be seen best in FIGS. 13A and 13B.

Further, the test element 110 may comprise a first electrode contactzone 138 and a second electrode contact zone 146 configured to contactthe first electrode 116 and the second electrode 118 with a furtherdevice, e.g., to a measurement device 172. The first electrode contactzone 138 and/or the second electrode contact zone 146 and the side doseposition 164 and front dose position 166 may be arranged at opposingends of the test element 110. The first electrode contact zone 138 andthe second electrode contact zone 146 may be arranged in differentlayers of the layer setup of the test element 110. The first electrodecontact zone 138 and the second electrode contact zone 146 may beconfigured to be electrically contacted from opposing sides of the testelement 110.

The first electrode conductive layer 120 and the first electrode carrierlayer 122 may form an overhang on the contact side of the test element110 over the second electrode conductive layer 148 and the secondelectrode carrier layer 150. Thus, parts of the first electrodeconductive layer 120 may be exposed and may allow contacting the firstelectrode 116 with the further device.

As described above, the spacer layer 134 may be designed such that itdoes not extend over the full length of the test element 110. The spacerlayer 134 may comprise at least one hole and/or at least one recess,which may have an arbitrary form, for example circular or rectangular.The spacer layer 134 may be formed in one part or in multiple parts. Thespacer layer 134 may be formed in two parts, wherein the two parts maybe aligned with a gap 208 in between. The second electrode contact zone146 may be formed in the following way: The first electrode conductivelayer 120 and the first electrode carrier layer 122 may comprise atleast one hole and/or at least one recess, which may have an arbitraryform, for example circular or rectangular. For example, recesses in thefirst electrode conductive layer 120 and the first electrode carrierlayer 122 may be formed by cutting and/or punching. In this embodiment,two rectangular recesses 210 may be present in the first electrodeconductive layer 120 and the first electrode carrier layer 122. Thespacer layer 134 may be arranged such that, within the layer setup ofthe test element 110, the spacer layer 134 may not cover recesses 210.Thus, parts of the second electrode conductive layer 148 may be exposedand may allow contacting the second electrode 118 with the furtherdevice, e.g., measurement device 172.

LIST OF REFERENCE NUMBERS

-   110 test element-   112 carrier element-   114 adhesive layer-   116 first electrode-   118 second electrode-   120 first electrode conductive layer-   122 first electrode carrier layer-   124 first longitudinal edge-   126 second longitudinal edge-   128 reagent coating-   130 longitudinal axis-   132 strip handle-   134 spacer layer-   136 adhesive layer-   138 first electrode contact zone-   140 measurement zone-   142 conductive material layer-   144 conductive adhesive layer-   146 second electrode contact zone-   148 second electrode conductive layer-   150 second electrode carrier layer-   151 conductive adhesive layer-   152 strip of Ag/AgCl paste-   154 first longitudinal edge-   156 second longitudinal edge-   158 arrows-   160 capillary-   161 gap-   162 cutting lines-   164 side dose position-   166 front dose position-   168 front face-   170 system-   172 measurement device-   174 side-   176 turnover element-   178 connector-   180 arrows-   182 arrow-   184 top dose position-   186 contact hole-   188 first portion-   189 adhesive layer-   190 second portion-   191 adhesive layer-   192 vent hole opening-   194 hydrophobic surface-   196 inner parts-   198 outer parts-   200 Arrow-   202 aluminum layer-   204 stripe of carbon-   205 adhesive layer-   206 adhesive layer-   208 gap-   210 recess

It is noted that terms like “preferably”, “commonly”, and “typically”are not utilized herein to limit the scope of the claimed subject matteror to imply that certain features are critical, essential, or evenimportant to the structure or function of the embodiments disclosedherein. Rather, these terms are merely intended to highlight alternativeor additional features that may or may not be utilized in a particularembodiment of the present disclosure.

It is noted that the terms “substantially” and “about” are utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus, it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modifications and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A system for determining at least one property ofa sample, the system comprising at least one test element, wherein thetest element comprises at least one first electrode and at least onesecond electrode, wherein the first electrode is designed as a workingelectrode and the second electrode is designed as a counter electrode,wherein the test element comprises at least one capillary capable ofreceiving a sample of the body fluid, wherein the first electrode andthe second electrode are arranged on opposing sides of the capillary,wherein the first electrode and the second electrode and the capillaryin between the first electrode and the second electrode form anelectrochemical cell, wherein the test element is configured to detectthe at least one analyte independently of a filling level of theelectrochemical cell, wherein the first electrode and the secondelectrode are arranged such that during a capillary filling the firstelectrode and the second electrode are wetted simultaneously and at anequal rate, the system further comprising at least one measurementdevice adapted for performing at least one electrical measurement usingthe test element, wherein the measurement device is configured to detectboth an AC signal and a DC signal, and wherein the measurement device isconfigured to detect the at least one analyte independently of a fillinglevel of the electrochemical cell.
 2. The system according to claim 1,wherein the measurement device is further configured to electricallymonitor a filling process of the capillary.
 3. The system according toclaim 1, wherein the measurement device is configured to perform atleast one initial failsafe measurement before applying the sample ofbodily fluid.
 4. A method for determining at least one property of asample, wherein a system according to claim 1 is used, wherein themethod comprises the following steps: a) connecting the test element toat least one measurement device; b) applying a sample of bodily fluid toa capillary of at least one test element; c) determining both an ACsignal and a DC signal with said measurement device; and d) calibratingmeasurement results by using the AC and DC signal.
 5. The methodaccording to claim 4, wherein the AC signal and the DC signal aredetermined simultaneously by said measurement device.
 6. The methodaccording to claim 4, wherein the determination of the AC and DC signalis performed by overlapping excitation potentials.
 7. The methodaccording to claim 4, wherein both the AC signal and the DC signal areproportional to the filling level of the capillary such that effects dueto a filling of the capillary are compensated.
 8. The method accordingto claim 4, wherein the method further comprises determining a contacttime, wherein an AC signal is applied between at least one firstelectrode and at least one second electrode of the test element, whereina response over time is measured, and wherein the response is comparedto a predefined threshold.
 9. The method according to claim 4, whereinthe method further comprises determining a filling level of thecapillary, wherein an AC signal is applied between the at least onefirst electrode and the at least one second electrode of the testelement, wherein a response signal over time is measured, wherein theresponse is compared to at least one predefined threshold, and whereinthe predetermined threshold is chosen such that a minimum filling levelis ensured.
 10. The method according to claim 9, wherein the predefinedthreshold is chosen with respect to a specific conductivity of a sample.11. The method according to claim 4, wherein the method furthercomprises monitoring a filling process of the capillary, wherein a DCvoltage is applied between the first electrode and the second electrode,wherein a DC response is detected, and wherein the DC response iscompared to a predefined limit.
 12. A test element for electrochemicallydetecting at least one analyte in a bodily fluid, wherein the testelement comprises at least one first electrode and at least one secondelectrode, wherein the first electrode is designed as a workingelectrode and the second electrode is designed as a counter electrode,wherein the test element comprises at least one capillary capable ofreceiving a sample of the body fluid, wherein the first electrode andthe second electrode are arranged on opposing sides of the capillary,wherein the first electrode and the second electrode and the capillaryin between the first electrode and the second electrode form anelectrochemical cell, wherein the test element is configured to detectthe at least one analyte independently of a filling level of theelectrochemical cell, wherein the first electrode and the secondelectrode are arranged such that during a capillary filling the firstelectrode and the second electrode are wetted simultaneously and at anequal rate, wherein the capillary is open at three sides, wherein asample of bodily fluid is applicable to one or both of a side doseposition or a front dose position, wherein the test element comprises afirst electrode contact zone and a second electrode contact zoneconfigured to contact the first electrode and the second electrode witha further device, wherein the first electrode contact zone and thesecond electrode contact zone are arranged in different layers of alayer setup of the test element, wherein one of the first electrodecontact zone and the second electrode contact zone protrudes over theother one of the first electrode contact zone and the second electrodecontact zone, wherein the first electrode contact zone and the secondelectrode contact zone are configured to be electrically contacted fromopposing sides of the test element, wherein the test element comprises alayer setup, wherein the first electrode comprises at least one firstelectrode conductive layer disposed on at least one first electrodecarrier layer, wherein the second electrode comprises at least onesecond electrode conductive layer disposed on at least one secondelectrode carrier layer, and wherein at least one spacer layer isdisposed in between the first electrode conductive layer and the secondelectrode conductive layer.
 13. The test element according to claim 12,wherein the test element has an elongated shape extending along alongitudinal axis, wherein the capillary at least partially extendsperpendicular to the longitudinal axis, and wherein the capillaryextends from a first opening at a first longitudinal edge of the testelement to a second opening at a second longitudinal edge of the testelement.
 14. A method for producing a test element according to claim12, the method comprising at least one step of forming a layer setup,wherein the first electrode, the second electrode and the capillary areformed such that the first electrode and the second electrode arearranged on opposing sides of the capillary, wherein the test element isproduced in a continuous process and the method further comprisingcutting the layer setup into test strips.